Image processing method, and image processor

ABSTRACT

The present invention provides an image processing method which includes any one of recording an image on a thermally reversible recording medium that can reversibly change any one of its transparency and color tone depending on temperature by irradiating and heating the thermally reversible recording medium with a laser beam, and erasing the image recorded on the thermally reversible recording medium by heating the thermally reversible recording medium, wherein in any one of the image recording and the image erasing, the thermally reversible recording medium is located at a position farther than a focal position of the laser beam, and at least any one of the image recording and the image erasing is performed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image processing method and an imageprocessor that can be suitably used in the image processing method.

2. Description of the Related Art

Until now, an image have been recorded and erased on a thermallyreversible recording medium (hereinafter, may be referred to as“recording medium” or “medium” merely) by a contact method in which thethermally reversible recording medium is heated by making contact with aheat source. For the heat source, in the case of image recording, athermal head is generally used, and in the case of image erasing, a heatroller, a ceramic heater or the like is generally used.

Such a contact type recording method has advantages in that when athermally reversible recording medium is composed of a flexible materialsuch as film and paper, an image can be uniformly recorded and erased byevenly pressing a heat source against the thermally reversible recordingmedium with use of a platen, and an image recording device and an imageerasing device can be produced at cheap cost by using components of aconventional thermosensitive printer.

However, when a thermally reversible recording medium incorporates anRF-ID tag as described in Japanese Patent Application Laid-Open (JP-A)Nos. 2004-265247 and 2004-265249, the thickness of the thermallyreversible recording medium is naturally thickened and the flexibilitythereof is degraded. Therefore, to evenly press a heat source againstthe thermally reversible recording medium, it needs a high-pressure.Further, when there are convexoconcave or irregularities on the surfaceof a thermally reversible recording medium, it becomes difficult torecord and erase an image using a thermal head or the like. In view ofthe fact that RF-ID tag enables reading and rewriting of memoryinformation from some distance away from a thermally reversiblerecording medium in a non-contact manner, a demand arises for thermallyreversible recording media as well. The demand is that an image orimages be rewritten on such a thermally reversible recording medium fromsome distance away from the thermally reversible recording medium.

To respond to the demand, a recording method using a non-contact laseris proposed as a method of recording and erasing each image on athermally reversible recording medium from some distance away from thethermally reversible recording medium when there are convexoconcave orirregularities on the surface thereof.

As such a recording method using a laser, a recording device (lasermaker) is proposed of which a thermally reversible recording medium isirradiated with a highly energized laser beam to control the irradiationposition. A thermally reversible recording medium is irradiated with alaser beam using the laser marker, the recording medium absorbs light,the light is converted into heat, a phase change is generated on therecording medium by effect of heat, thereby an image can be recorded anderased.

When an image is recorded using the laser marker, generally, the imageis recorded at a focal position where a laser beam is condensed andenergy concentration is the highest. At the focal position, the spotdiameter of the laser beam is the smallest, and when a character isrecorded at the focal position, the character is composed of thin lines.Therefore, the visibility may be insufficient. Further, when the imageis erased using a laser beam, image displacement may occur to causeerasing residue due to the small spot diameter of the laser beam at thefocal position. There is a problem that when a laser beam is extensivelyscanned so as not to cause such erasing residue, it takes a long time toerase an image.

To solve the problem, for example, Japanese Patent Application Laid-Open(JP-A) Nos. 2002-347272 and 2003-161907 respectively propose expandingthe spot diameter of a laser beam using a mirror. Japanese PatentApplication Laid-Open (JP-A) No. 2000-71088 proposes expanding the spotdiameter of a laser beam by controlling a distance between a concavelens and a convex lens. However, these techniques require mounting aspot diameter changing unit to a laser recording device. Therefore, thelaser recording device is naturally increased in size, resulting in ahigh cost. Further, JP-A Nos. 2003-161907 and 2000-71088 respectivelydisclose a laser marker capable of directly recording a lot number, amodel number etc. on a workpiece material such as metal and plastic.

Further, in the technique described in JP-A No. 2002-347272, when alaser beam is scanned using a scanning mirror, a thermally reversiblerecording medium is located so as to be closer than the focal positionto thereby expand the spot diameter of the laser beam. Therefore, wheneach image is recorded and erased at that position, the scanningdistance of a scanning mirror is longer than the scanning distance wheneach image is recorded and erased at the focal point, and it takeslonger time to record and erase each image. Further, when a thermallyreversible recording medium is located so as to be closer than the focalposition, there is a problem that recorded regions and erased regionsbecome narrower.

A laser marker is configured to record each image by irradiating aregion to be recorded with a laser beam by scanning the laser beam whilechanging a laser beam irradiation direction by changing a scanningmirror angle with motor actuation. In a generally used recording device,it is ideal that irradiation conditions are set such that theirradiation power and the scanning speed of a laser are constant and thelaser beam is applied to a recording medium such that a same temperatureis maintained in regions to be recorded.

However, for example, in characters of “V”, “Y”, “E”, “X”, etc., atleast any of image line among a plurality of image lines has an overlapportion or overlap portions. Because of repeated recording at theoverlap portion on a thermally reversible recording medium, an excessiveamount of energy is applied to the overlap portion, and it may sometimesdamage the thermally reversible recording medium. Further, at a startpoint of an image line, the irradiation power of the laser beam maybecome unstable because of incapability of controlling the irradiationpower, and an excessive irradiation power may be sometimes applied tothe thermally reversible recording medium (overshooting). Further, whenan image line is folded at an overlap portion, it is difficult toinstantaneously change a mirror angle by means of mortar actuation, andthus the scanning speed of the laser beam is lowered, and an excessiveamount of energy is applied to the overlap portion. Therefore, there isa problem that a thermally reversible recording medium is damaged byrepeatedly recording and erasing an image. Further, when scanning alaser beam using an XY stage instead of a scanning mirror, the scanningspeed is decelerated due to acceleration and deceleration operationsduring a time period from a stopped state of the XY stage until the XYstage begins to be actuated or during a time period from an actuatedstate of the XY stage until the XY stage is stopped. For this reason,similarly to the case of using a scanning mirror, an excessive amount ofenergy is applied to start points and end points of a recorded image,and there may be cases where the thermally reversible recording mediumis damaged.

A laser marker is configured to record each image by irradiating aregion to be recorded with a laser beam by scanning the laser beam whilechanging a laser beam irradiation direction by changing a scanningmirror angle with motor actuation. In a generally used recording device,it is ideal that irradiation conditions are set such that at least anyone of the irradiation power and the scanning speed of a laser isconstant and the laser beam is applied to a recording medium such that asame temperature is maintained in regions to be recorded.

However, at a start point of an image line, the irradiation power of thelaser beam may become unstable because of incapability of controllingthe irradiation power, and an excessive irradiation power may besometimes applied to the thermally reversible recording medium(overshooting).

During a time period from a stopped state of the scanning mirror untilthe scanning mirror begins to be actuated or during a time period froman actuated state of the scanning mirror until the scanning mirror isstopped, the scanning speed is decelerated due to acceleration anddeceleration operations. For this reason, the scanning speed of thescanning mirror is decelerated at a recording start point (start point),a recording end point (end point) and a folded point where therotational direction of the scanning mirror is changed, and an excessiveamount of energy is applied to these points, and there may be caseswhere the thermally reversible recording medium is damaged due torepeated recording and erasing. Further, when scanning a laser beamusing an XY stage instead of a scanning mirror, the scanning speed isdecelerated due to acceleration and deceleration operations during atime period from a stopped state of the XY stage until the XY stagebegins to be actuated or during a time period from an actuated state ofthe XY stage until the XY stage is stopped. For this reason, similarlyto the case of using a scanning mirror, an excessive amount of energy isapplied to a start point and an end point of a recorded image, and theremay be cases where the thermally reversible recording medium is damaged.

On these points, even when an excessive amount of energy is applied to aconventional non-reversible heat-sensitive recording medium, this doesnot become a major problem, however, on a thermally reversible recordingmedium where each image is repeatedly recorded and erased, there is alarge problem that an excessive amount of energy is applied to the sameportions to cause damage to the recording medium, and each image cannotbe uniformly recorded at high-image density and cannot be uniformlyerased due to accumulation of damage.

To solve these problems, for example, Japanese Patent ApplicationLaid-Open (JP-A) No. 2003-127446 describes that when an image isrecorded on a thermally reversible recording medium so that record dotsoverlap each other or when an image is recorded with folding lines,laser irradiation energy is controlled for every imaging points toreduce energy to be given to these portions; and also describes thatwhen straight lines are recorded, local thermal damage is reduced byreducing energy at every certain intervals to thereby preventdeterioration of the thermally reversible recording medium.

Japanese Patent Application Laid-Open (JP-A) No. 2004-345273 describes atechnique of reducing energy by multiplying irradiation energy by thefollowing expression in accordance with an angle R where a laser beamangle is changed when an image is recorded using a laser.

|cos 0.5R| ^(k)(0.3<k<4)

With use of this technique, it is possible to prevent an excessiveamount of energy from being given to overlap portions in line imageswhen an image is recorded using a laser and to prevent deterioration ofa recording medium or to maintain an image contrast without excessivelyreducing the energy.

Further, Japanese Patent Application Laid-Open (JP-A) No. 2006-306063proposes a recording method in which when a certain image is recorded byirradiating a non-contact type rewrite thermal label with a focusedlaser beam, a light scanning device is continuously driven withoutoscillating the laser beam, and only when a trajectory of the laser beamassumed when the laser beam is oscillated (a virtual laser beam) movesat a substantially constant speed, the laser beam is oscillated to scanthe laser beam and to record the image on the non-contact type rewritethermal label.

These conventional recording methods respectively provide a technique inwhich an excessive amount of thermal energy is not to be applied to athermally reversible recording medium at overlap portions when recordingan image using a laser. However, when a uniform image is recorded athigh-density and erased repeatedly by using a highly energized laser,not only a start point, an end point and a folding portion of an imageline but also the center portion of a straight line are excessivelyheated, deformed sites and air bubbles are observed on the surface ofthe thermally reversible recording medium, and materials themselves eachexhibiting color developing-color erasing properties are thermallydecomposed, and these materials cannot exert their sufficient ability.As a result, on the entire image lines including start points, endpoints, folding portions and straight lines constituting an image, it isimpossible to uniformly record the image with high-image density and isimpossible to uniformly erase the image on a sufficient level, and as animage processing method that causes less deterioration of a thermallyreversible recording medium even when the image is repeatedly recordedand erased, there is much to be desired, and further improvements anddevelopments are still desired.

BRIEF SUMMARY OF THE INVENTION

First, the present invention aims to provide an image processing methodthat allows for shortening a scanning direction of a scanning mirror andshortening recording time and erasing time than in recording and erasingan image at a position nearer than a focal position of a laser beam usedor at the focal position and widening a recording area and an erasingarea by placing a thermally reversible recording medium at a positionfarther than the focal position of the laser beam and performing any oneof image recording and image erasing, and also to provide an imageprocessor that can be suitably used in the image processing method.

Secondarily, the present invention aims to provide an image processingmethod that enables preventing an excessive amount of energy from beingapplied to the entire image lines including start points, end points,folding points and straight lines constituting an image and enablespreventing deterioration of a thermally reversible recording medium byreducing damage attributable to repeated recording and erasing of eachimage, and also to provide an image processor that can be preferablyused in the image processing method.

Thirdly, the present invention aims to provide an image processingmethod that enables an image to be uniformly recorded and erased athigh-image density for the entire image lines including start points,end points, folding points and straight lines constituting an image andenables preventing deterioration of a thermally reversible recordingmedium by reducing damage attributable to repeated recording and erasingof each image, and to also provide an image processor that can bepreferably used in the image processing method.

Means to solve the above-noted problems are as follows.

<1> An image processing method, including any one of recording an imageon a thermally reversible recording medium that can reversibly changeany one of its transparency and color tone depending on temperature byirradiating and heating the thermally reversible recording medium with alaser beam, and erasing the image recorded on the thermally reversiblerecording medium by heating the thermally reversible recording medium,wherein in any one of the image recording and the image erasing, thethermally reversible recording medium is located at a position fartherthan a focal position of the laser beam, and at least any one of theimage recording and the image erasing is performed.

<2> The image processing method according to the item <1>, wherein whena distance from a condenser lens to the focal position is represented by“X” and a distance from the condenser lens to the thermally reversiblerecording medium is represented by “Y”, the equation, Y/X=1.02 to 2.0,is satisfied.

<3> The image processing method according to any one of the items <1> to<2>, wherein when a spot diameter of the laser beam at the focalposition is represented by “A” and a spot diameter of the laser beam onthe thermally reversible recording medium is represented by “B”, theequation, B/A=1.5 to 76, is satisfied.

<4> The image processing method according to any one of the items <1> to<3>, used in image recording and image erasing on a movable object.

<5> An image processing method including any one of recording an imageon a thermally reversible recording medium that can reversibly changeany one of its transparency and color tone depending on temperature byirradiating and heating the thermally reversible recording medium with alaser beam, and erasing the image recorded on the thermally reversiblerecording medium by heating the thermally reversible recording medium,wherein in the image recording, when an image having an overlap portionor overlap portions where a plurality of image lines are overlapped witheach other is to be recorded, each of the image lines is recorded in anoncontinuous manner at the overlap portion.

<6> The image processing method according to the item <5>, wherein theimage is recorded so that at least one of a start point and an end pointof each of the image lines is overlapped with another image line at theoverlap portion.

<7> The image processing method according to any one of the items <5> to<6>, wherein the image is recorded so that an end point of each of theimage lines is overlapped with an end point of another image line at theoverlap portion.

<8> The image processing method according to any one of the items <5> to<7>, wherein the image is recorded so that a start point of each of theimage lines is not overlapped with another image line.

<9> An image processing method including any one of recording an imageon a thermally reversible recording medium that can reversibly changeany one of its transparency and color tone depending on temperature byirradiating and heating the thermally reversible recording medium with alaser beam, and erasing the image recorded on the thermally reversiblerecording medium by heating the thermally reversible recording medium,wherein in the image recording, at least one of a scanning speed and anirradiation power of the laser beam is controlled such that at least oneof a laser beam irradiation energy per unit time and a laser beamirradiation energy per unit area in the thermally reversible recordingmedium is substantially constant.

<10> The image processing method according to the item <9>, wherein atleast one of the scanning speed and the irradiation power of the laserbeam is controlled such that at least one of the laser beam irradiationenergy per unit time and the laser beam irradiation energy per unit areaat a start point, an end point, and a folding point of each of aplurality of image lines constituting an image is substantiallyconstant.

<11> The image processing method according to any one of the items <9>to <10>, wherein at least one of the scanning speed and the irradiationpower of the laser beam is controlled such that a value of P/V, where“P” represents an irradiation power of the laser beam on the thermallyreversible recording medium, and “V” represents a scanning speed of thelaser beam on the thermally reversible recording medium, issubstantially constant.

<12> The image processing method according to any one of the items <9>to <11>, wherein data of at least one of the scanning speed and theirradiation power of the laser beam controlled such that at least one ofthe laser beam irradiation energy per unit time and the laser beamirradiation energy per unit area in the thermally reversible recordingmedium is substantially constant is previously stored, and then theimage is recorded based on the data.

<13> The image processing method according to any one of the items <1>to <12>, wherein each of the plurality of image lines is a lineconstituting any one of a character, a symbol and a diagram.

<14> The image processing method according to any one of the items <1>to <13>, wherein the thermally reversible recording medium has at leasta thermally reversible recording layer on a substrate, and the thermallyreversible recording layer reversibly changes any one of itstransparency and color tone at between a first specific temperature anda second specific temperature that is higher than the first specifictemperature.

<15> The image processing method according to any one of the items <1>to <14>, wherein the thermally reversible recording medium has at leasta reversible thermosensitive recording layer on a substrate, and thereversible thermosensitive recording layer contains a resin and anorganic low-molecular material.

<16> The image processing method according to any one of the items <1>to <14>, wherein the thermally reversible recording medium has at leasta reversible thermosensitive recording layer on a substrate, and thereversible thermosensitive recording layer contains a leuco dye and areversible developer.

<17> The image processing method according to any one of the items <1>to <16>, wherein in a light intensity distribution of the laser beamirradiated in any one of the image recording and the image erasing, alight irradiation intensity I₁ at a center position of the irradiatedlaser beam and a light irradiation intensity I₂ on an 80% light energybordering surface to the total light energy of the irradiated laser beamsatisfy the expression, 0.40≦I₁/I₂≦2.00.

<18> An image processor having at least a laser beam emitting unit, anda light irradiation intensity controlling unit that is placed on a laserbeam emitting surface and is configured to change the light irradiationintensity of a laser beam, wherein the image processor is used in animage processing method according to any one of the items <1> to <17>.

<19> The image processor according to the item 18, wherein the lightirradiation intensity controlling unit is at least any one of a lens, afilter, a mask, a mirror and a fiber-coupling device.

A first embodiment of the image processing method of the presentinvention includes any one of recording an image on a thermallyreversible recording medium that can reversibly change any one of itstransparency and color tone depending on temperature by irradiating andheating the thermally reversible recording medium with a laser beam, anderasing the image recorded on the thermally reversible recording mediumby heating the thermally reversible recording medium, wherein in any oneof the image recording and the image erasing, the thermally reversiblerecording medium is located at a position farther than a focal positionof the laser beam, and at least any one of the image recording and theimage erasing is performed.

In the image processing method according to the first embodiment of thepresent invention, by placing the thermally reversible recording mediumat a position farther than a focal position of the laser beam andperforming at least any one of image recording and image erasing, ascanning distance of a scanning mirror can be shortened and therecording time and erasing time can be shortened as compared to the casewhere each image is recorded and erased at a position nearer than thefocal position or at the focal position. Further, since the thermallyreversible recording medium is placed at a position farther than thefocal position, a recording area and an erasing area can be widened.

A second embodiment of the image processing method of the presentinvention includes any one of recording an image on a thermallyreversible recording medium that can reversibly change any one of itstransparency and color tone depending on temperature by irradiating andheating the thermally reversible recording medium with a laser beam, anderasing the image recorded on the thermally reversible recording mediumby heating the thermally reversible recording medium, wherein in theimage recording, when an image having an overlap portion or overlapportions where a plurality of image lines are overlapped with each otheris to be recorded, the each image line is recorded at the overlapportion in a noncontinuous manner.

In the image processing method according to the second embodiment of thepresent invention, in the image recording step, when an image having anoverlap portion or overlap portions where a plurality of image lines areoverlapped with each other is to be recorded, the each image line isrecorded at the overlap portion in a noncontinuous manner. Even when anoverlap portion is folded just as seen in, for example, a character “V”and a character “F”, the image processing method can prevent anexcessive amount of energy being applied to the overlap portion andprevent deterioration of the thermally reversible recording medium byreducing damage due to repeated image recording and image erasing.

A third embodiment of the image processing method of the presentinvention includes any one of recording an image on a thermallyreversible recording medium that can reversibly change any one of itstransparency and color tone depending on temperature by irradiating andheating the thermally reversible recording medium with a laser beam, anderasing the image recorded on the thermally reversible recording mediumby heating the thermally reversible recording medium, wherein in theimage recording, at least one of a scanning speed and an irradiationpower of the laser beam is controlled such that at least one of thelaser beam irradiation energy per unit time and the laser beamirradiation energy per unit area in the thermally reversible recordingmedium is substantially constant.

In the image processing method according to the third embodiment of thepresent invention, an energy amount to be applied to a thermallyreversible recording medium is constant, and it is possible to preventan excessive amount of energy from being applied to start points, endpoints and folding points of image lines constituting an image, touniformly record an image at high-density and uniformly erase therecorded image on the entire image lines including the start points, theend points, the folding points and further straight points of the imagelines constituting the image and to prevent deterioration of thethermally reversible recording medium by reducing damage due to repeatedimage recording and image erasing.

The image processor of the present invention is used in any one of theimage processing methods according to first embodiment to the thirdembodiment of the present invention, and has at least a laser beamemitting unit and a light irradiation intensity controlling unit that isplaced on a laser beam emitting surface of the laser beam emitting unitand is configured to change a light irradiation intensity of a laserbeam.

In the image processor, the laser beam emitting unit is configured toemit a laser beam, and the light irradiation intensity controlling unitis configured to change a light irradiation intensity of the laser beamemitted from the laser beam emitting unit. As a result, when an image isrecorded on the thermally reversible recording medium, it is possible toshorten recording time and erasing time and to widen a recording areaand an erasing area.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view showing one example of a laser irradiationdevice.

FIG. 2 is a schematic view showing another example of a laserirradiation device.

FIG. 3A is a schematic illustration showing one example of a lightintensity distribution of an irradiated laser beam used in the presentinvention.

FIG. 3B is a schematic illustration showing a light intensitydistribution (Gauss distribution) of a commonly used laser beam.

FIG. 3C is a schematic illustration showing one example of a lightintensity distribution obtained when a light intensity of a laser beamis changed.

FIG. 3D is a schematic illustration showing another example of a lightintensity distribution obtained when a light intensity of a laser beamis changed.

FIG. 3E is a schematic illustration showing still another example of alight intensity distribution obtained when a light intensity of a laserbeam is changed.

FIG. 4A is an illustration showing one example of a method of recordinga character “V” in the image recording step in the image processingmethod of the present invention.

FIG. 4B is an illustration showing another example of a method ofrecording a character “V” in the image recording step in the imageprocessing method of the present invention.

FIG. 4C is an illustration showing one example of a method of recordinga character “V” in an image recording step in a conventional imageprocessing method.

FIG. 5A is an illustration showing one example of a method of recordinga character “Y” in the image recording step in the image processingmethod of the present invention.

FIG. 5B is an illustration showing another example of a method ofrecording a character “Y” in the image recording step in the imageprocessing method of the present invention.

FIG. 5C is an illustration showing one example of a method of recordinga character “Y” in an image recording step in a conventional imageprocessing method.

FIG. 5D is an illustration showing another example of a method ofrecording a character “Y” in an image recording step in a conventionalimage processing method.

FIG. 5E is an illustration showing still another example of a method ofrecording a character “Y” in an image recording step in a conventionalimage processing method.

FIG. 5F is an illustration showing still yet another example of a methodof recording a character “Y” in an image recording step in aconventional image processing method.

FIG. 5G is an illustration showing still yet another example of a methodof recording a character “Y” in an image recording step in aconventional image processing method.

FIG. 5H is an illustration showing still yet another example of a methodof recording a character “Y” in an image recording step in aconventional image processing method.

FIG. 6A is an illustration showing one example of a method of recordinga character “F” in the image recording step in the image processingmethod of the present invention.

FIG. 6B is an illustration showing another example of a method ofrecording a character “F” in the image recording step in the imageprocessing method of the present invention.

FIG. 6C is an illustration showing still another example of a method ofrecording a character “F” in the image recording step in the imageprocessing method of the present invention.

FIG. 6D is an illustration showing still yet another example of a methodof recording a character “F” in the image recording step in the imageprocessing method of the present invention.

FIG. 6E is an illustration showing one example of a method of recordinga character “F” in an image recording step in a conventional imageprocessing method.

FIG. 6F is an illustration showing another example of a method ofrecording a character “F” in an image recording step in a conventionalimage processing method.

FIG. 6G is an illustration showing still another example of a method ofrecording a character “F” in an image recording step in a conventionalimage processing method.

FIG. 6H is an illustration showing still yet another example of a methodof recording a character “F” in an image recording step in aconventional image processing method.

FIG. 7A is an illustration showing one example of a method of recordinga character “X” in the image recording step in the image processingmethod of the present invention.

FIG. 7B is an illustration showing another example of a method ofrecording a character “X” in the image recording step in the imageprocessing method of the present invention.

FIG. 7C is an illustration showing still another example of a method ofrecording a character “X” in the image recording step in the imageprocessing method of the present invention.

FIG. 7D is an illustration showing still yet another example of a methodof recording a character “X” in the image recording step in the imageprocessing method of the present invention.

FIG. 7E is an illustration showing still yet another example of a methodof recording a character “X” in the image recording step in the imageprocessing method of the present invention.

FIG. 7F is an illustration showing one example of a method of recordinga character “X” in an image recording step in an image processing methodaccording to a comparative aspect.

FIG. 7G is an illustration showing another example of a method ofrecording a character “X” in an image recording step in an imageprocessing method according to another comparative aspect.

FIG. 8 is an illustration schematically showing a relation between timeand irradiation power of a laser beam.

FIG. 9 is an illustration schematically showing a relation between timeand scanning speed of a laser beam.

FIG. 10 is an illustration showing one example of a method of recordinga character “V” in the image recording step in the image processingmethod of the present invention.

FIG. 11A is a graph showing transparency-white turbidity property of athermally reversible recording medium of the present invention.

FIG. 11B is a schematic illustration showing a mechanism of a changebetween transparency and white turbidity of a thermally reversiblerecording medium of the present invention.

FIG. 12A is a graph showing color developing-color erasing property of athermally reversible recording medium.

FIG. 12B is a schematic illustration showing a mechanism of a changebetween color developing and color erasing of a thermally reversiblerecording medium of the present invention.

FIG. 13 is a schematic illustration showing one example of an RF-ID tag.

FIG. 14A is a schematic illustration showing one example of a lightirradiation intensity controlling unit used in an image processor of thepresent invention.

FIG. 14B is a schematic illustration showing another example of a lightirradiation intensity controlling unit used in an image processor of thepresent invention.

FIG. 15 is a schematic illustration showing one example of an imageprocessor of the present invention.

DETAILED DESCRIPTION OF THE INVENTION (Image Processing Method)

The image processing method of the present invention includes at leastan image recording step and an image erasing step and further includesother steps suitably selected in accordance with necessity.

The image processing method of the present invention contains all theaspects including an aspect in which both image recording and imageerasing are performed, an aspect in which only image recording isperformed, and an aspect in which only image erasing is performed.

<Image Recording Step and Image Erasing Step>

The image recording step in the image processing method of the presentinvention is a step in which an image is recorded by irradiating with alaser beam and heating a thermally reversible recording medium that canreversibly change any one of its transparency and color tone dependingon temperature.

The image erasing step in the image processing method of the presentinvention is a step in which the image recorded on the thermallyreversible recording medium is erased by irradiating and heating thethermally reversible recording medium with a laser beam.

In the image erasing step of the image processing method in the presentinvention, images recorded on the thermally reversible recording mediumare erased by heating the thermally reversible recording medium, and asa heat source, a laser beam may be used or other heat sources other thanlaser beam may be used. Among a variety of heat sources, when thethermally reversible recording medium is irradiated with a laser beam toheat the thermally reversible recording medium and an image recorded onthe thermally reversible recording medium is erased in a short time, itis preferable to use an infrared lamp, a heat roller, a hot stamp, adrier or the like to heat it because it takes some time to scan thethermally reversible recording medium with a single laser beam toirradiate the entire given area. Further, when the thermally reversiblerecording medium is attached to a styrofoam box as a conveyancecontainer used in a logistical line and the styrofoam box itself isheated, the styrofoam box is melted, and thus it is preferable that onlythe thermally reversible recording medium be irradiated with a laserbeam to locally heat thereof.

By irradiating with the laser beam and heating the thermally reversiblerecording medium, an image can be recorded and erased on the thermallyreversible recording medium in a non-contact manner.

Note that in the image processing method of the present invention,typically, an image is renewed for the first time (the image erasingstep) when the thermally reversible recording medium is reused, andthereafter, another image is recorded in the image recording step,however, the order of image recording and image erasing is not limitedthereto. Thus, an image may be recorded in the image recording step, andthereafter the image may be erased in the image erasing step.

Image Processing Method according to Third Embodiment

In the image processing method according to the first embodiment of thepresent invention, in any one of the image forming step and the imageerasing step, the thermally reversible recording medium is located at aposition farther than a focal position of the laser beam, and at leastany one of the image recording and the image erasing is performed. Whenthe thermally reversible recording medium is located at a positionfarther than a focal position of the laser beam and an image isrecorded, in the image erasing step, the thermally reversible recordingmedium is not necessarily located at a position farther than the focalposition of the laser beam, and a heat source other than laser beams maybe used. Among a variety of heat sources, when the thermally reversiblerecording medium is irradiated with a laser beam to heat the thermallyreversible recording medium and an image recorded on the thermallyreversible recording medium is erased in a short time, it is preferableto use an infrared lamp, a heat roller, a hot stamp, a drier or the liketo heat it because it takes some time to scan the thermally reversiblerecording medium with a single laser beam to irradiate the entire givenarea. Further, when the thermally reversible recording medium isattached to a styrofoam box as a conveyance container used in alogistical line and the styrofoam box itself is heated, the styrofoambox is melted, and thus it is preferable that only the thermallyreversible recording medium be irradiated with a laser beam to locallyheat thereof.

Further, when the thermally reversible recording medium is located at aposition farther than a focal position of the laser beam and an image isrecorded, in the image recording step, the thermally reversiblerecording medium is not necessarily located at a position farther thanthe focal position of the laser beam, for example, heat sources otherthan laser beams such as thermal head may be used as a heat source.

Here, as shown in FIG. 1, a laser beam 103 emitted from a laser device100 concentrated by a lens 105, energy density reaches a maximum at afocal position 101. However, the spot diameter of the laser beam becomesthe smallest at the focal position 101, and thus when a character isrecorded at the focal position 101, the character is constituted by thinlines at the focal position 101, and the visibility may be sometimesinsufficient. When the recorded image is erased using a laser beam, thespot diameter of the laser beam is small at the focal position, and thuswhen a displacement occurs, erasing residue may occur. In the meanwhile,there is a problem that when the laser beam is scanned in a wide area soas not to cause erasing residue, it takes some time to erase the image.

FIG. 2 is an illustration showing a case where a laser beam irradiatedfrom a laser device 100 is scanned in a predetermined recording areausing a scanning mirror. In FIG. 2, the thermally reversible recordingmedium is placed at a position 104 nearer than a focal position 101.When an image is recorded and erased at the position 104, a scanningdistance from the scanning mirror becomes longer than the scanningdistance obtained when the image is recorded and erased at the focalposition 101, consequently, it takes some time to record and erase theimage. Further, there is another problem that when a thermallyreversible recording medium is placed at a position nearer than thefocal position, a recording area and an erasing area become narrow.

Then, in the first embodiment of the image processing method of thepresent invention, in at least one of the image recording step and theimage erasing step, the thermally reversible recording medium is placedat a position farther than a focal position of the laser beam and thenat least one of image recording and image erasing is performed. In onlyone of the image recording step or the image erasing step, a thermallyreversible recording medium may be placed at a position farther than thefocal position of the laser beam, however, it is preferable that athermally reversible recording medium be placed at a position fartherthan the focal position of the laser beam in both the image recordingstep and the image erasing step. With this configuration, a scanningdistance of the scanning mirror can be shortened, a recording time andan erasing time can be shortened, and the recording area and the erasingarea can be further widened as compared to in the case where an image isrecorded and erased at a position nearer than the focal position or atthe focal position.

Specifically, when a distance from a condenser lens to a focal positionis represented by “X” and a distance from the condenser lens to athermally reversible recording medium is represented by “Y”, it ispreferable that the equation, Y/X=1.02 to 2.0, be satisfied, and it ismore preferable that the equation, Y/X=1.025 to 1.5. When the value ofY/X is less than 1.02, a recorded character is constituted by thinlines, and the visibility may be sometimes insufficient. When the valueof Y/X is more than 2.0, a laser output power required to heat thethermally reversible recording medium to a certain temperature isincreased, resulting in an increase of the device in size. When thescanning speed is decelerated to heat the thermally reversible recordingmedium to a certain temperature without increasing a laser output power,it may take some time to record and erase an image.

In the image recording step, it is preferable that the value of Y/Xsatisfy the equation, Y/X=1.02 to 1.2. In the image erasing step, it ispreferable that the value of Y/X satisfy the equation, Y/X=1.05 to 2.0.

The distance Y from the laser light source to the thermally reversiblerecording medium is not particularly limited and may be suitablyselected in accordance with the intended use, however, it is preferably51 mm to 600 mm and more preferably 52 mm to 450 mm.

Further, in the present invention, when the spot diameter of a laserbeam at a focal point is represented by “A” and the spot diameter of thelaser beam on the thermally reversible recording medium is representedby “B”, it is preferable that the equation, B/A=1.5 to 76, be satisfiedand more preferable that the equation, B/A 3.0 to 38, be satisfied. Whenthe value of B/A is less than 1.5, a recorded character is constitutedby thin lines, and the visibility may be sometimes insufficient. Whenthe value of B/A is more than 76, a laser output power required to heatthe thermally reversible recording medium to a certain temperature isincreased, resulting in an increase of the device in size. When thescanning speed is decelerated to heat the thermally reversible recordingmedium to a certain temperature without increasing a laser output power,it may take some time to record and erase an image.

Further, in the image recording step, it is preferable that the value ofB/A satisfy the equation, B/A=1.5 to 20. In the image erasing step, itis preferable that the value of B/A satisfy the equation, B/A=3.0 to 76.

The spot diameter B of the laser beam on the thermally reversiblerecording medium is not particularly limited and may be suitablyselected in accordance with the intended use, however, it is preferably0.02 mm to 14.0 mm and more preferably 0.06 mm to 7.0 mm.

Here, in general, in a light intensity distribution of a laser beam,which is a Gauss distribution, a diameter being 1/e² of the centerintensity is called a spot diameter (or a spot size, beam diameteretc.), and 86.5% of the total light quantity is contained in the spotdiameter, however, in the present invention, a diameter in which 86.5%of the total light quantity is contained is defined as a spot diameter,instead of using the diameter being 1/e² of the center intensity.

A method of placing a thermally reversible recording medium at aposition farther than a focal position of a laser beam as describedabove is not particularly limited and may be suitably selected inaccordance with the intended use. Examples of the method include (1) amethod of which a laser device is fixed, and the position of a thermallyreversible recording medium is changed; (2) a method of which theposition of a thermally reversible recording medium is fixed, and theposition of a laser beam is changed; (3) a method of using a combinationof the method (1) and the method (2); and a method of extending anoptical path of a laser beam using an optical path extension mirror.

For the method (1) of changing the position of a thermally reversiblerecording medium, for example, a method is exemplified in which thethermally reversible recording medium is set to a stage, and the stageis moved.

For the method (2) of changing the position of a laser device, forexample, a method is exemplified in which the laser device is set to astage, and the stage is moved.

Since the image processing method according to the first embodiment ofthe present invention allows for shortening recording time and erasingtime and widening a recording area and an erasing area, the imageprocessing method can be particularly preferably used for relativelylarge bar codes, moving objects (movable objects), andlogistical/physical distribution systems. For example, an image can beefficiently recorded and erased on a thermally reversible recordingmedium (a label) while moving a corrugated fiberboard placed on a beltconveyer. Thus, the image processing method enables shortening shippingtime because there is no need to stop production lines. The corrugatedfiberboard with the label attached thereto can be reused just as it iswithout peeling off the label, and an image can be erased and recordedagain on the corrugated fiberboard.

Image Processing Method According to Second Embodiment

In the second embodiment of the image processing method of the presentinvention, in the image recording step, when an image having an overlapportion or overlap portions where a plurality of image lines areoverlapped with each other is to be recorded, the each image line isrecorded at the overlap portion in a noncontinuous manner.

When each of image lines is recorded in a continuous manner at theoverlap portion, for example, when an image line is folded at an overlapportion, it is difficult to instantaneously change a mirror angle bymeans of mortar actuation, and thus the scanning speed of the laser beamis lowered, an excessive amount of energy is applied to the overlapportion, and the thermally reversible recording medium may be locallydamaged by repeatedly recording and erasing the image. Examples of anaspect in which each of image lines are recorded in a continuous mannerat the overlap portion include an aspect in which each image is recordedsuch that an end point of the each image line is overlapped with an endpoint of another image line at the overlap portion.

Here, “the recording in a non-continuous manner” means that during atime of recording a plurality of image lines by laser irradiation, thelaser beam irradiation is stopped once, and the plurality of image linesare individually recorded. Specific examples of such an aspect include(1) an aspect in which each image is recorded such that an end point ofeach image line is overlapped with an end point of another image line atthe overlap portion; (2) an aspect in which each image is recorded suchthat a start point of each image line is overlapped with a start pointof another image line at the overlap portion; (3) an aspect in which animage is recorded such that a start point of each image line isoverlapped with a portion of another image line other than a start pointand an end point of the another image line (for example, an intermediatepoint of another image line) at the overlap portion; and (4) an aspectin which an image is recorded such that an end point of each image lineis overlapped with a portion of another image line other than a startpoint and an end point of the another image line (for example, anintermediate point of another image line) at the overlap portion; orcombinations of the above combinations.

At a start pint of the image line, the laser beam irradiation powerbecomes instable because of incapability of controlling, and anexcessive amount of irradiation power may be applied to the thermallyreversible recording medium (overshooting). For this reason, it ispreferable to record an image such that a start point of each image isnot overlapped with another image line at the overlap portion.

It is preferable that the image line be a line constituting any one of acharacter, a symbol and a diagram.

Hereinafter, the cases where a character “V” is recorded will bedescribed with reference to FIGS. 4A to 4C.

FIG. 4A is an illustration showing one example of a method of recordinga character “V” in the image recording step in the image processingmethod of the present invention.

First, a thermally reversible recording medium is irradiated with alaser beam, and an image line 1 is recorded in a D1 direction. Here,irradiation of the laser beam is stopped, the focal point of the laserbeam irradiation is moved to a start point of an image line 2, and thenthe image line 2 is recorded in a D2 direction. As a result, in therecording of a character “V” illustrated in FIG. 4A, since the end pointof the image line 1 and the end point of the image line 2 are overlappedwith each other at a folded overlap portion T, and the image line 1 andthe image line 2 are separately recorded in a non-continuous manner, anexcessive amount of energy is not applied to the overlap portion T, anddamage is not caused to the thermally reversible recording medium evenwhen the image is repeatedly recorded and erased. Note that in FIG. 4A,the order of recording the image line 1 and the image line 2 may bereversed.

FIG. 4B is an illustration showing another example of a method ofrecording a character “V” in the image recording step in the imageprocessing method of the present invention. First, a thermallyreversible recording medium is irradiated with a laser beam, and animage line 1 is recorded in a D3 direction. Here, irradiation of thelaser beam is stopped, the focal point of the laser beam irradiation ismoved to a start point of an image line 2 (an overlap portion T), andthen the image line 2 is recorded in a D4 direction. As a result, in therecording method illustrated in FIG. 4B, since the start point of theimage line 1 and the start point of the image line 2 are overlapped witheach other at a folded overlap portion T, and the image line 1 and theimage line 2 are separately recorded in a non-continuous manner, anexcessive amount of energy is not applied to the overlap portion T, anddamage is not caused to the thermally reversible recording medium evenwhen the image is repeatedly recorded and erased. Note that in FIG. 4B,the order of recording the image line 1 and the image line 2 may bereversed.

Note that in the recording method illustrated in FIG. 4B, since theoverlap portion T is the start point of the image lines of 1 and 2, theirradiation power of the laser beam may become unstable because ofincapability of controlling the irradiation power, and an excessiveirradiation power may be sometimes applied to the thermally reversiblerecording medium. Thus, an excessive amount of energy is possiblyapplied to an overlap portion as compared to the recording methodillustrated in FIG. 4A. Therefore, when a character “V” is to berecorded, the recording method as illustrated in FIG. 4A is the mostpreferable.

In contrast to the above-mentioned recording methods, FIG. 4C is anillustration showing one example of a method of recording a character“V” in an image recording step in a conventional image processingmethod. First, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 1 is recorded in a D1 direction.Then, an image line 2 is recorded in a D4 direction with beingcontinuously recorded at an overlap portion T. Specifically, in therecording of a character “V” as illustrated in FIG. 4C, the end point ofthe image line 1 is overlapped with the start point of the image line 2at the folded overlap portion T, and the image lines 1 and 2 arecontinuously recorded. At the folded overlap portion T, the scanningdirection of the laser beam is changed by changing a mirror angle bymotor actuation, and thus the scanning speed of the laser beam at theoverlap portion T is decelerated. As a result, an excessive amount ofenergy is applied to the overlap portion T, resulting in damage to thethermally reversible recording medium because of the repeated imagerecording and image erasing.

Further, the cases where a character “Y” is recorded will be describedwith reference to FIGS. 5A to 5H.

FIG. 5A is an illustration showing one example of a method of recordinga character “Y” in the image recording step in the image processingmethod of the present invention. First, a thermally reversible recordingmedium is irradiated with a laser beam, and an image line 11 is recordedin a D1 direction. Here, irradiation of the laser beam is stopped, thefocal point of the laser beam irradiation is moved to a start point ofan image line 12, and the image line 12 is recorded in a D2 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 13,and the image line 13 is recorded in a D3 direction. As a result, in therecording of a character “Y” as illustrated in FIG. 5A, since the endpoint of the image line 11, the end point of the image line 12 and theend point of the image line 13 are overlapped with each other at anoverlap portion T where the image lines 11, 12 and 13 are separatelyrecorded in a non-continuous manner, an excessive amount of energy isnot applied to the overlap portion T, and damage is not caused to thethermally reversible recording medium even when the image is repeatedlyrecorded and erased. Note that in FIG. 5A, the order of recording theimage lines 11, 12 and 13 is not particularly limited and may besuitably selected.

Further, FIG. 5B is an illustration showing another example of a methodof recording a character “Y” in the image recording step in the imageprocessing method of the present invention. First, a thermallyreversible recording medium is irradiated with a laser beam, and animage line 11 is recorded in a D4 direction. Here, irradiation of thelaser beam is stopped, the focal point of the laser beam irradiation ismoved to a start point of an image line 12 (an overlap portion T), andthe image line 12 is recorded in a D5 direction. Here, irradiation ofthe laser beam is stopped, the focal point of the laser beam irradiationis moved to a start point of an image line 13 (the overlap portion T),and the image line 13 is recorded in a D6 direction. As a result, in therecording of a character “Y” as illustrated in FIG. 5B, since the startpoint of the image line 11, the start point of the image line 12 and thestart point are overlapped with each other at the overlap portion Twhere the three image lines are overlapped, and the image lines 11, 12and 13 are separately recorded in a non-continuous manner, an excessiveamount of energy is not applied to the overlap portion T, and damage isnot caused to the thermally reversible recording medium even when theimage is repeatedly recorded and erased. Note that in FIG. 5B, the orderof recording the image lines 11, 12 and 13 is not particularly limitedand may be suitably selected.

Note that in the recording method illustrated in FIG. 5B, since theoverlap portion T is the start point of the three image lines, theirradiation power of the laser beam may become unstable because ofincapability of controlling the irradiation power, and an excessiveirradiation power may be sometimes applied to the thermally reversiblerecording medium. Thus, an excessive amount of energy is possiblyapplied to an overlap portion as compared to the recording methodillustrated in FIG. 5A. Therefore, when a character “Y” is to berecorded, the recording method as illustrated in FIG. 5A is the mostpreferable.

In contrast to the above-mentioned recording methods, FIGS. 5C to 5Hshow other examples of a method of recording a character “Y” in an imagerecording step in a conventional image processing method.

In FIG. 5C, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 11 is recorded in a D1 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 12 in a D5 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 13 (anoverlap portion T), and the image line 13 is recorded in a D3 direction.Specifically, in the recording of a character “Y” as illustrated in FIG.5C, the end point of the image line 11 is overlapped with the startpoint of the image line 12 at the overlap portion T where the threeimage lines are overlapped, and the image lines 11 and 12 arecontinuously recorded. At the folded overlap portion T, the scanningdirection of the laser beam is changed by changing a mirror angle bymotor actuation, and thus the scanning speed of the laser beam at theoverlap portion T is decelerated. As a result, an excessive amount ofenergy is applied to the overlap portion T, resulting in damage to thethermally reversible recording medium because of the repeated imagerecording and image erasing.

In FIG. 5D, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 11 is recorded in a D1 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 12 in a D5 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 13(the overlap portion T), and the image line 13 is recorded in a D6direction. Specifically, in the recording of a character “Y” asillustrated in FIG. 5D, the end point of the image line 11 is overlappedwith the start point of the image line 12 at the overlap portion T wherethe three image lines are overlapped, and the image lines 11 and 12 arecontinuously recorded. At the folded overlap portion T, the scanningdirection of the laser beam is changed by changing a mirror angle bymotor actuation, and thus the scanning speed of the laser beam at theoverlap portion T is decelerated. As a result, an excessive amount ofenergy is applied to the overlap portion T, resulting in damage to thethermally reversible recording medium because of the repeated imagerecording and image erasing.

Note that the image line 11 may be recorded first, continuously, theimage line 13 may be recorded, and thereafter, the image line 12 may berecorded.

In FIG. 5E, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 11 is recorded in a D1 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 13 in a D6 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 12,and the image line 12 is recorded in a D2 direction. Specifically, inthe recording of a character “Y” as illustrated in FIG. 5E, the endpoint of the image line 11 is overlapped with the start point of theimage line 13 at the overlap portion T where the three image lines areoverlapped, and the image lines 11 and 13 are continuously recorded. Atthe folded overlap portion T, the scanning direction of the laser beamis changed by changing a mirror angle by motor actuation, and thus thescanning speed of the laser beam at the overlap portion T isdecelerated. As a result, an excessive amount of energy is applied tothe overlap portion T, resulting in damage to the thermally reversiblerecording medium because of the repeated image recording and imageerasing.

In FIG. 5F, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 12 is recorded in a D2 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 13 in a D6 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 11 (anoverlap portion T), and the image line 11 is recorded in a D4 direction.Specifically, in the recording of a character “Y” as illustrated in FIG.5F, the end point of the image line 12 is overlapped with the startpoint of the image line 13 at the overlap portion T where the threeimage lines are overlapped, and the image lines 12 and 13 arecontinuously recorded. At the folded overlap portion T, the scanningdirection of the laser beam is changed by changing a mirror angle bymotor actuation, and thus the scanning speed of the laser beam at theoverlap portion T is decelerated. As a result, an excessive amount ofenergy is applied to the overlap portion T, resulting in damage to thethermally reversible recording medium because of the repeated imagerecording and image erasing.

Note that the image line 12 may be recorded first, continuously, theimage line 11 may be recorded, and thereafter, the image line 13 may berecorded.

In FIG. 5G, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 13 is recorded in a D3 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 12 in a D5 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 11 (anoverlap portion T), and the image line 11 is recorded in a D4 direction.Specifically, in the recording of a character “Y” as illustrated in FIG.5G, the end point of the image line 13 is overlapped with the startpoint of the image line 12 at the overlap portion T where the threeimage lines are overlapped, and the image lines 13 and 12 arecontinuously recorded. At the folded overlap portion T, the scanningdirection of the laser beam is changed by changing a mirror angle bymotor actuation, and thus the scanning speed of the laser beam at theoverlap portion T is decelerated. As a result, an excessive amount ofenergy is applied to the overlap portion T, resulting in damage to thethermally reversible recording medium because of the repeated imagerecording and image erasing.

Note that the image line 13 may be recorded first, continuously, theimage line 11 may be recorded, and thereafter, the image line 12 may berecorded.

In FIG. 5H, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 13 is recorded in a D3 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 11 in a D4 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 12,and the image line 12 is recorded in a D2 direction. Specifically, inthe recording of a character “Y” as illustrated in FIG. 5F, the endpoint of the image line 13 is overlapped with the start point of theimage line 11 at the overlap portion T where the three image lines areoverlapped, and the image lines 13 and 11 are continuously recorded. Atthe folded overlap portion T, the scanning direction of the laser beamis changed by changing a mirror angle by motor actuation, and thus thescanning speed of the laser beam at the overlap portion T isdecelerated. As a result, an excessive amount of energy is applied tothe overlap portion T, resulting in damage to the thermally reversiblerecording medium because of the repeated image recording and imageerasing.

Further, the cases where a character “F” is recorded will be describedwith reference to FIGS. 6A to 6H.

FIG. 6A shows one example of a method of recording a character “F” inthe image recording step in the image processing method of the presentinvention. First, a thermally reversible recording medium is irradiatedwith a laser beam, and an image 21 is recorded in a D1 direction. Here,irradiation of the laser beam is stopped, the focal point of the laserbeam irradiation is moved to a start point of an image line 22, and theimage line 22 is recorded in a D2 direction. Here, irradiation of thelaser beam is stopped, the focal point of the laser beam irradiation ismoved to a start point of an image line 23 (an overlap portion T2), andthe image line 23 is recorded in a D3 direction. Specifically, in therecording of a character “F” as illustrated in FIG. 6A, the end point ofthe image line 21 is overlapped with the end point of the image line 22at a folded overlap portion T1, an intermediate portion of the imageline 21 is overlapped with the start point of the image line 23 at theoverlap portion T2, and the image lines 21, 22 and 23 are separatelyrecorded in a non-continuous manner. Thus, an excessive amount of energyis not applied to the overlap portions T1 and T2, and damage is notcaused to the thermally reversible recording medium even when the imageis repeatedly recorded and erased. Note that in FIG. 6A, the order ofrecording the image line 21 and the image line 22 may be reversed.

FIG. 6B shows another example of a method of recording a character “F”in the image recording step in the image processing method of thepresent invention. First, a thermally reversible recording medium isirradiated with a laser beam, and an image line 21 is recorded in a D1direction. Here, irradiation of the laser beam is stopped, the focalpoint of the laser beam irradiation is moved to a start point of animage line 22, and the image line 22 is recorded in a D2 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 23,and the image line 23 is recorded in a D4 direction. Specifically, inthe recording of a character “F” as illustrated in FIG. 6B, the endpoint of the image line 21 is overlapped with the end point of the imageline 22 at a folded overlap portion T1, an intermediate portion of theimage line 21 is overlapped with the end point of the image line 23 atan overlap portion T2, and the image lines 21, 22 and 23 are separatelyrecorded in a non-continuous manner. Thus, an excessive amount of energyis not applied to the overlap portions T1 and T2, and damage is notcaused to the thermally reversible recording medium even when the imageis repeatedly recorded and erased. Note that in FIG. 6B, the order ofrecording the image line 21 and the image line 22 may be reversed.

FIG. 6C shows still another example of a method of recording a character“F” in the image recording step in the image processing method of thepresent invention. First, a thermally reversible recording medium isirradiated with a laser beam, and an image line 21 is recorded in a D5direction. Here, irradiation of the laser beam is stopped, the focalpoint of the laser beam irradiation is moved to a start point of animage line 22 (an overlap portion T1), and the image line 22 is recordedin a D6 direction. Here, irradiation of the laser beam is stopped, thefocal point of the laser beam irradiation is moved to a start point ofan image line 23 (an overlap portion T2), and the image line 23 isrecorded in a D3 direction. Specifically, in the recording of acharacter “F” as illustrated in FIG. 6C, the stat point of the imageline 21 is overlapped with the start point of the image line 22 at theoverlap portion T1, an intermediate portion of the image line 21 isoverlapped with the start point of the image line 23 at the overlapportion T2, and the image lines 21, 22 and 23 are separately recorded ina noncontinuous manner. Thus, an excessive amount of energy is notapplied to the overlap portions T1 and T2, and damage is not caused tothe thermally reversible recording medium even when the image isrepeatedly recorded and erased. Note that in FIG. 6C, the order ofrecording the image line 21 and the image line 22 may be reversed.

FIG. 6D shows still yet another example of a method of recording acharacter “F” in the image recording step in the image processing methodof the present invention. First, a thermally reversible recording mediumis irradiated with a laser beam, and an image line 21 is recorded in aD5 direction. Here, irradiation of the laser beam is stopped, the focalpoint of the laser beam irradiation is moved to a start point of animage line 22 (an overlap portion T1), and the image line 22 is recordedin a D6 direction. Here, irradiation of the laser beam is stopped, thefocal point of the laser beam irradiation is moved to a start point ofan image line 23, and the image line is recorded in a D4 direction.Specifically, in the recording of a character “F” as illustrated in FIG.6D, the start point of the image line 21 is overlapped with the startpoint of the image line 22 at the folded overlap portion T1, anintermediate portion of the image line 21 is overlapped with the endpoint of the image line 23 at overlap portion T2, and the image lines21, 22 and 23 are separately recorded in a non-continuous manner. Thus,an excessive amount of energy is not applied to the overlap portions T1and T2, and damage is not caused to the thermally reversible recordingmedium even when the image is repeatedly recorded and erased. Note thatin FIG. 6D, the order of recording the image line 21 and the image line22 may be reversed.

As compared between FIG. 6A and FIG. 6B, in the recording methodillustrated in FIG. 6B, the respective start points of the image linesare not overlapped at the overlap portions, however, in the recordingmethod illustrated in FIG. 6A, the start point of the image line 23 isoverlapped with the image line 21 at the overlap portion T2. Therefore,in FIG. 6A, the irradiation power of the laser beam may become unstablebecause of incapability of controlling the irradiation power, and anexcessive irradiation power is possibly applied to the overlap portionT2.

Further, in FIG. 6C and FIG. 6D, the start point of the image line 21 isoverlapped with the start point of the image line 22 at the overlapportion T1. The irradiation power of the laser beam may become unstablebecause of incapability of controlling the irradiation power, and anexcessive irradiation power is possibly applied to the overlap portionT2.

Thus, when a character “F” is to be recorded, the recording method asillustrated in FIG. 6B is the most preferable.

In contrast to the above-mentioned recording methods, FIGS. 6E to 6Hshow other examples of a method of recording a character “F” in an imagerecording step in a conventional image processing method.

In FIG. 6E, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 21 is recorded in a D1 direction.The laser beam is continuously irradiated while passing an overlapportion T1 to continuously record an image line 22 in a D6 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 23 (anoverlap portion T2), and the image line 23 is recorded in a D3direction. Specifically, in the recording of a character “F” asillustrated in FIG. 6E, the end point of the image line 21 is overlappedwith the start point of the image line 22 at the folded overlap portionT1, and the image lines 21 and 22 are continuously recorded. At thefolded overlap portion T1, the scanning direction of the laser beam ischanged by changing a mirror angle by motor actuation, and thus thescanning speed of the laser beam at the overlap portion T1 isdecelerated. As a result, an excessive amount of energy is applied tothe overlap portion T1, resulting in damage to the thermally reversiblerecording medium because of the repeated image recording and imageerasing.

At the overlap portion T2, since an intermediate portion of the imageline 21 is overlapped with the start point of the image line 23 and theimage lines 21 and 23 are recorded in a non-continuous manner, anexcessive amount of energy is not applied to the overlap portion T2, anddamage is not caused to the thermally reversible recording medium due torepeated recording.

In FIG. 6F, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 21 is recorded in a D1 direction.The laser beam is continuously irradiated while passing an overlapportion T1 to continuously record an image line 22 in a D6 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 23,and the image line 23 is recorded in a D4 direction. Specifically, inthe recording of a character “F” as illustrated in FIG. 6F, the endpoint of the image line 21 is overlapped with the start point of theimage line 22 at the folded overlap portion T1, and the image lines 21and 22 are continuously recorded. At the folded overlap portion T1, thescanning direction of the laser beam is changed by changing a mirrorangle by motor actuation, and thus the scanning speed of the laser beamat the overlap portion T1 is decelerated. As a result, an excessiveamount of energy is applied to the overlap portion T1, resulting indamage to the thermally reversible recording medium because of therepeated image recording and image erasing.

At the overlap portion T2, since an intermediate portion of the imageline 21 is overlapped with the end point of the image line 23 and theimage lines 21 and 23 are recorded in a non-continuous manner, anexcessive amount of energy is not applied to the overlap portion T2, anddamage is not caused to the thermally reversible recording medium due torepeated recording.

In FIG. 6G, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 22 is recorded in a D2 direction.The laser beam is continuously irradiated while passing an overlapportion T1 to continuously record an image line 21 in a D5 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 23 (anoverlap portion T2), and the image line 23 is recorded in a D3direction. Specifically, in the recording of a character “F” asillustrated in FIG. 6G, the end point of the image line 22 is overlappedwith the start point of the image line 21 at the folded overlap portionT1, and the image lines 22 and 21 are continuously recorded. At thefolded overlap portion T1, the scanning direction of the laser beam ischanged by changing a mirror angle by motor actuation, and thus thescanning speed of the laser beam at the overlap portion T1 isdecelerated. As a result, an excessive amount of energy is applied tothe overlap portion T1, resulting in damage to the thermally reversiblerecording medium because of the repeated image recording and imageerasing.

At the overlap portion T2, since an intermediate portion of the imageline 21 is overlapped with the start point of the image line 23 and theimage lines 21 and 23 are recorded in a non-continuous manner, anexcessive amount of energy is not applied to the overlap portion T2, anddamage is not caused to the thermally reversible recording medium due torepeated recording.

In FIG. 6H, a thermally reversible recording medium is irradiated with alaser beam, and an image line 22 is recorded in a D2 direction. Thelaser beam is continuously irradiated while passing an overlap portionT1 to continuously record an image line 21 in a D5 direction. Here,irradiation of the laser beam is stopped, the focal point of the laserbeam irradiation is moved to a start point of an image line 23, and theimage line 23 is recorded in a D4 direction. Specifically, in therecording of a character “F” as illustrated in FIG. 6H, the end point ofthe image line 22 is overlapped with the start point of the image line21 at the folded overlap portion T1, and the image lines 22 and 21 arecontinuously recorded. At the folded overlap portion T1, the scanningdirection of the laser beam is changed by changing a mirror angle bymotor actuation, and thus the scanning speed of the laser beam at theoverlap portion T1 is decelerated. As a result, an excessive amount ofenergy is applied to the overlap portion T1, resulting in damage to thethermally reversible recording medium because of the repeated imagerecording and image erasing.

At the overlap portion T2, since an intermediate portion of the imageline 21 is overlapped with the end point of the image line 23 and theimage lines 21 and 23 are recorded in a non-continuous manner, anexcessive amount of energy is not applied to the overlap portion T2, anddamage is not caused to the thermally reversible recording medium due torepeated recording.

Further, the cases where a character “X” is recorded will be describedwith reference to FIGS. 7A to 7G.

FIG. 7A shows one example of a method of recording a character “X” inthe image recording step in the image processing method of the presentinvention. First, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 32 is recorded in a D2 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 31 a,and the image line 31 a is recorded in a D1 direction. Here, irradiationof the laser beam is stopped, the focal point of the laser beamirradiation is moved to a start point of an image line 31 b, and theimage line 31 b is recorded in a D3 direction. Specifically, in therecording of a character “X” as illustrated in FIG. 7A, the end point ofthe image line 31 a, the end point of the image line 31 b and anintermediate point of the image line 32 are overlapped at an overlapportion T, and the image lines 32, 31 a and 31 b are separately recordedin a non-continuous manner. Thus, an excessive amount of energy is notapplied to the overlap portion T, and damage is not caused to thethermally reversible recording medium even when the image is repeatedlyrecorded and erased.

FIG. 7B shows another example of a method of recording a character “X”in the image recording step in the image processing method of thepresent invention. First, a thermally reversible recording medium isirradiated with a laser beam, and an image line 32 is recorded in a D2direction. Here, irradiation of the laser beam is stopped, the focalpoint of the laser beam irradiation is moved to a start point of animage line 31 a (an overlap portion T), and the image line 31 a isrecorded in a D4 direction. Here, irradiation of the laser beam isstopped, the focal point of the laser beam irradiation is moved to astart point of an image line 31 b (the overlap portion T), and the imageline 31 b is recorded in a D5 direction. Specifically, in the recordingof a character “X” as illustrated in FIG. 7B, the start point of theimage line 31 a, the start point of the image line 31 b and anintermediate point of the image line 32 are overlapped at the overlapportion T, and the image lines 32, 31 a and 31 b are separately recordedin a non-continuous manner. Thus, an excessive amount of energy is notapplied to the overlap portion T, and damage is not caused to thethermally reversible recording medium even when the image is repeatedlyrecorded and erased.

FIG. 7C shows still another example of a method of recording a character“X” in the image recording step in the image processing method of thepresent invention. First, a thermally reversible recording medium isirradiated with a laser beam, and an image line 31 is recorded in a D1direction. Here, irradiation of the laser beam is stopped, the focalpoint of the laser beam irradiation is moved to a start point of animage line 32 a, and the image line 32 a is recorded in a D2 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 32 b,and the image line 32 b is recorded in a D6 direction. Specifically, inthe recording of a character “X” as illustrated in FIG. 7C, the endpoint of the image line 32 a, the end point of the image line 32 b andan intermediate pint of the image line 31 are overlapped at an overlapportion T, and the image lines 31, 32 a and 32 b are separately recordedin a non-continuous manner. Thus, an excessive amount of energy is notapplied to the overlap portion T, and damage is not caused to thethermally reversible recording medium even when the image is repeatedlyrecorded and erased.

FIG. 7D shows still yet another example of a method of recording acharacter “X” in the image recording step in the image processing methodof the present invention. First, a thermally reversible recording mediumis irradiated with a laser beam, and an image line 31 is recorded in aD1 direction. Here, irradiation of the laser beam is stopped, the focalpoint of the laser beam irradiation is moved to a start point of animage line 32 a (an overlap portion T), and the image line 32 a isrecorded in a D7 direction. Here, irradiation of the laser beam isstopped, the focal point of the laser beam irradiation is moved to astart point of an image line 32 b (the overlap portion T), and the imageline 32 b is recorded in a D8 direction. Specifically, in the recordingof a character “X” as illustrated in FIG. 7D, the start point of theimage line 32 a, the start point of the image line 32 b and anintermediate point of the image line 31 are overlapped at the overlapportion T, and the image lines 31, 32 a and 32 b are separately recordedin a non-continuous manner. Thus, an excessive amount of energy is notapplied to the overlap portion T, and damage is not caused to thethermally reversible recording medium even when the image is repeatedlyrecorded and erased.

FIG. 7E shows still yet another example of a method of recording acharacter “X” in the image recording step in the image processing methodof the present invention. First, a thermally reversible recording mediumis irradiated with a laser beam, and an image line 31 is recorded in aD1 direction. Here, irradiation of the laser beam is stopped, the focalpoint of the laser beam irradiation is moved to a start point of animage line 32, and the image line 32 is recorded in a D2 direction.Specifically, in the recording of a character “X” as illustrated in FIG.7E, in the overlap portion T, the image line 31 is overlapped with theimage line 32 at intermediate points thereof, and the image lines 31 and32 are separately recorded in a non-continuous manner. However, anexcessive amount of energy required for recording two times is appliedto the overlap portion T when recording once, resulting in slightlydamaging the thermally reversible recording medium due to repeated imagerecording and image erasing, as compared to the recording methods asillustrated in FIGS. 7A to 7D, where at least one of a start point andan end of each of image lines is overlapped with another image line.

Note that in FIG. 7E, the order of recording the image line 31 and theimage line 32 may be reversed.

In contrast to the above-mentioned recording methods, FIGS. 7F and 7Grespectively show one example of a method of recording a character “X”in an image recording step in an image processing method according to acomparative aspect.

In FIG. 7F, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 31 a is recorded in a D1 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 32 b in a D8 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 32 a,and the image line 32 a is recorded in a D2 direction. The laser beam iscontinuously irradiated while passing the overlap portion T tocontinuously record an image line 31 b in a D5 direction. Specifically,in the recording of a character “X” as illustrated in FIG. 7F, the imagelines 31 a and 32 b are continuously recorded at the overlap portion T,and the image lines 32 a and 31 b are continuously recorded at theoverlap portion T. At the overlap portion T, the scanning direction ofthe laser beam is changed by changing a mirror angle by motor actuation,and thus the scanning speed of the laser beam at the overlap portion Tis decelerated. As a result, an excessive amount of energy is applied tothe overlap portion T, resulting in damage to the thermally reversiblerecording medium because of the repeated image recording and imageerasing.

Note that the order of recording the image lines 31 a and 32 b and theimage lines 32 a and 31 b may be reversed.

In FIG. 7G, first, a thermally reversible recording medium is irradiatedwith a laser beam, and an image line 32 b is recorded in a D6 direction.The laser beam is continuously irradiated while passing an overlapportion T to continuously record an image line 31 a in a D4 direction.Here, irradiation of the laser beam is stopped, the focal point of thelaser beam irradiation is moved to a start point of an image line 32 a,and the image line 32 a is recorded in a D2 direction. The laser beam iscontinuously irradiated while passing the overlap portion T tocontinuously record an image line 32 a in a D7 direction. Specifically,in the recording of a character “X” as illustrated in FIG. 7G, the imagelines 32 b and 31 a are continuously recorded at the overlap portion T,and the image lines 31 b and 32 a are continuously recorded at theoverlap portion T. At the overlap portion T, the scanning direction ofthe laser beam is changed by changing a mirror angle by motor actuation,and thus the scanning speed of the laser beam at the overlap portion Tis decelerated. As a result, an excessive amount of energy is applied tothe overlap portion T, resulting in damage to the thermally reversiblerecording medium because of the repeated image recording and imageerasing.

Note that the order of recording the image lines 32 b and 31 a and theimage lines 31 b and 32 a may be reversed.

In the above-mentioned recoding methods, recording of each of imagelines is controlled by controlling a laser light source and a lightirradiation intensity controlling device such as lens, filter, mask andmirror. Specifically, positioning of each of the image lines can becontrolled by changing a laser beam irradiation direction by changing amirror angle by motor actuation.

Image Processing Method According to Third Embodiment

In the image processing method according to the third embodiment of thepresent invention, in the image recording step, at least one of ascanning speed and an irradiation power of the laser beam is controlledsuch that at least one of the laser beam irradiation energy per unittime and the laser beam irradiation energy per unit area in thethermally reversible recording medium is substantially constant.

Here, as shown in FIG. 8, at each start point of each of image linesconstituting an image, the irradiation power (P) of the laser beam isset to be high. This is because at each of start points of each of imagelines, the irradiation power of the laser beam may become unstablebecause of incapability of controlling the irradiation power, and anexcessive irradiation power may be applied to the thermally reversiblerecording medium (overshooting).

Further, as shown in FIG. 9, at each of start points of each of imagelines, the scanning speed (V) of the laser beam is decelerated. This isbecause at each of start points of each of image lines, it takes acertain time for a scanning mirror to be actuated from a stoppage stateand move at a substantially constant speed, and a laser beam cannot bescanned at a constant linear velocity, and thus an excessive amount ofenergy is applied partially to the thermally reversible recordingmedium, resulting in damage to the thermally reversible recordingmedium.

Further, at a folding portion of an image line, it is difficult toinstantaneously change the scanning mirror angle and a laser beam cannotbe scanned at a certain linear velocity (illustration is omitted). Thus,an excessive amount of energy is applied partially to a thermallyreversible recording medium, resulting in damage to the thermallyreversible recording medium.

The image lines are preferably lines constituting any one of acharacter, a symbol and a diagram.

To remove the above-mentioned shortcomings, in the image processingmethod according to the third embodiment of the present invention, inthe image recording step, at least one of a scanning speed (V) and anirradiation power (P) of the laser beam is controlled such that at leastone of the laser beam irradiation energy per unit time and the laserbeam irradiation energy per unit area in the thermally reversiblerecording medium is substantially constant. In this case, since theirradiation energy of the laser beam is proportional to a value of P/V(“P” represents an irradiation power of a laser beam on a thermallyreversible recording medium, and “V” represents a scanning speed of alaser beam on a thermally reversible recording medium), at least one ofthe scanning speed (V) and the irradiation power (P) of the laser beammay be controlled such that the value of P/V is substantially constant.

At least one of the irradiation energy per unit time and the irradiationenergy per unit area of the laser beam in the thermally reversiblerecording medium varies depending on an image processor to be used andcannot be unequivocally defined, however, it is preferably 0.70 times to1.30 times an optimum conditional value and more preferably 0.85 timesto 1.15 times the optimum conditional value. Here, the optimumconditional value is a center value within an irradiation energy rangewhen recording each image in a state where both the recording qualityand erasing quality can be satisfied. The upper limit value of theirradiation energy can be determined by erasing quality, and the lowerlimit value of the irradiation energy can be determined by recordingquality.

The expression “substantially constant” means that the irradiationenergy of the laser beam is constant, and specifically, the fluctuationrange of the irradiation energy is within ±15%.

In this case, it is preferable that at least any one of a scanning speed(V) and an irradiation power (P) of a laser beam be controlled such thatat least one of irradiation energy per unit time and irradiation energyper unit area of a laser beam or (P/V) particularly at each start point,each end point, and each folding point of each of image lines in aplurality of image lines constituting an image is substantiallyconstant.

Depending on an image processor to be used, there may be cases where itis difficult to control both a scanning speed (V) and an irradiationpower (P) of a laser beam, and an irradiation energy of a laser beam or(P/V) can be kept constant by controlling any one of a scanning speed(V) and an irradiation power (P) of a laser beam.

Specifically, at least any one of irradiation energy per unit time andirradiation energy per unit area of a laser beam or (P/V) can be keptconstant at each folding point of each image line by reducing anirradiation power of the laser beam or increasing a scanning speed ofthe laser beam at each start point of each image line, or combiningthem.

Further, at least any one of irradiation energy per unit time andirradiation energy per unit area of a laser beam or (P/V) can be keptconstant at each start point of each image line by reducing anirradiation power of the laser beam or increasing a scanning speed ofthe laser beam at each folding point of each image line, or combiningthem.

A method of controlling a scanning speed of the laser beam is notparticularly limited and may be suitably selected in accordance with theintended use. For example, a method of controlling the number ofrevolutions of a motor that actuates operations of a scanning mirror isexemplified. The number of revolutions (rpm) of a motor can becontrolled by changing a rotational speed set to the motor betweenportions where it is difficult to control the number of revolutions ofthe motor, such as start points and folding points, and straightportions. However, when a start point is to be recorded, it takes sometime from zero value of rotational speed to reach a target speed. Inthis case, it is necessary to control an irradiation power or a timingof laser beam irradiation (irradiate a laser beam when the number ofrevolutions of the motor reaches a target speed).

A method of controlling an irradiation power of the laser beam is notparticularly limited and may be suitably selected in accordance with theintended use. Examples thereof include a method of changing a set valueof a laser beam irradiation power, and when using a pulse irradiationlaser, a method of controlling an irradiation power by adjusting a pulsetime length width.

As a method of changing a set value of the laser beam irradiation power,a method of changing a power set value depending on a region to berecorded is exemplified. As a method of controlling a laser beamirradiation power, irradiation energy can be controlled by anirradiation power by changing a time length width for emitting a pulsedepending on a region to be recorded.

A method of controlling a light irradiation intensity by means of thelight irradiation intensity controlling unit will be describedhereinafter in explanation for the image processor of the presentinvention.

A scanning speed (V) of the laser beam is not particularly limited aslong as a ratio of P/V is a substantially constant, and may be suitablyselected in accordance with the intended use. However, the scanningspeed (V) is preferably 100 mm/s or more, more preferably 200 mm/s ormore, and still more preferably 300 mm/s or more because when thescanning speed is slow, it becomes difficult to control the scanningspeed and irradiation power.

Further, the upper limit of the scanning speed of the laser beam is notparticularly limited and may be suitably selected in accordance with theintended use, however, it is preferably 10,000 mm/s or less, morepreferably 7,000 mm/s or less, and still more preferably 4,000 mm/s orless. When the scanning speed is more than 10,000 mm/s, there may be adifficulty in recording a uniform image.

The spot diameter of the laser beam is not particularly limited and maybe suitably selected in accordance with the intended use, however, it ispreferably 0.02 mm or more, more preferably 0.1 mm or more, and stillmore preferably 0.2 mm or more. The upper limit of the spot diameter ofthe laser beam is not particularly limited and may be suitably selectedin accordance with the intended use, however, it is preferably 3.0 mm orless, more preferably 2.0 mm or less, and still more preferably 1.0 mmor less.

The spot diameter is proportional to a width of a line to becolor-developed. When the spot diameter is small, the line width becomesnarrow and the contrast becomes low, resulting in a low-visibility. Whenthe spot diameter is large, the line width becomes thick, the contrastbecomes high, adjacent lines are overlapped with each other, resultingin incapability of printing small characters.

An irradiation power (P) of the laser beam is not particularly limitedas long as a value of P/V is substantially constant, and may be suitablyselected in accordance with the intended use, however, it is preferably0.70 times to 1.30 times an optimum conditional value and morepreferably 0.85 times to 1.15 times the optimum conditional value. Theoptimum conditional value is a center value within an irradiation energyrange when recording each image in a state where both the recordingquality and erasing quality can be satisfied. The upper limit value ofthe irradiation energy can be determined by erasing quality, and thelower limit value of the irradiation energy can be determined byrecording quality.

Further, each image can be extremely efficiently recorded bypreliminarily storing data on at least any one of a scanning speed andan irradiation power of a laser beam that is controlled such that atleast one of irradiation energy per unit time and irradiation energy perunit area or a value of P/V of a laser beam in a thermally reversiblerecording medium is substantially constant in an image processor andrecording the each image based on the data.

In the image processing method according to the first embodiment to thethird embodiment of the present invention, it is preferable that in alight intensity distribution of the laser beam irradiated in any one ofthe image recording step and the image erasing step, a light irradiationintensity I₁ at a center position of the irradiated laser beam and alight irradiation intensity I₂ on an 80% light energy bordering surfaceto the total light energy of the irradiated laser beam satisfy theexpression, 0.40≦I₁/I₂≦2.00.

In any one of the image recording step and the image erasing step, it ispreferable that the thermally reversible recording medium be irradiatedwith the laser beam so that in a light intensity distribution of thelaser beam, a light irradiation intensity I₁ at a center position of theirradiated laser beam and a light irradiation intensity I₂ on an 80%light energy bordering surface to the total light energy of theirradiated laser beam satisfy the expression, 0.40≦I₁/I₂≦2.00.

Here, the center position of the irradiated laser beam is a positionthat can be determined by dividing a sum of a product of a lightirradiation intensity at each position and a coordinate at the eachposition by a sum of light irradiation intensities at each of thepositions and can be represented by the following expression.

Σ(r_(i)×I_(i))/ΣI_(i)

In the expression, “r_(i)” represents a coordinate at each position,“I_(i)” represents a light irradiation intensity at the each position,and “ΣI_(i)” represents a sum of light irradiation intensities.

The total irradiation energy means the entire energy of a laser beamirradiated onto the thermally reversible recording medium.

Conventionally, when a pattern is formed using a laser, a lightintensity distribution on a cross-section in the perpendicular directionto the proceeding direction of a scanned laser beam (hereinafter, may bereferred to as “the proceeding direction”) is a Gauss distribution, andthe light intensity at a center position of the irradiated laser beam ismuch higher than the light irradiation intensity in peripheral portionsthereof. When the laser beam having a Gauss distribution is applied tothe thermally reversible recording medium and an image is repeatedlyformed and erased, a site of the recording medium corresponding to thecenter position of the irradiated laser beam deteriorates due toexcessively increased temperature at the center position, and the numberof repeatedly image recording and erasing times should be reduced.Further, when the laser irradiation energy is reduced so as not toincrease the temperature at the center position to a temperature atwhich the thermally reversible recording medium could deteriorate, itmay cause problems with a reduction in image size, a reduction incontrast, and taking much time in image formation.

Then, in the image processing method of the present invention, in alight intensity distribution on a cross-section in a substantiallyperpendicular direction to the proceeding direction of the laser beamirradiated in the image recording step, the light irradiation intensityat a center position in the light intensity distribution is controlledso as to be lower than the light irradiation intensity in peripheralportions thereof, in contrast to a Gauss distribution. With thisconfiguration, the image processing method achieves an improvement inrepetitive durability of a thermally reversible recording medium whilepreventing deterioration of the thermally reversible recording mediumattributable to repeated recording and erasing, as well as maintainingan image contrast, but without necessity of reducing the image in size.

Here, when a light intensity distribution of the irradiated laser beamis separated so that a horizontal plane in a perpendicular direction tothe proceeding direction occupies 20% of the total energy and includes amaximum value, and when a light intensity on the horizontal plane isrepresented by I₂ and a light intensity at the center position of thelight intensity in the irradiated laser beam is represented by I₁, alight intensity ratio I₁/I₂ of a Gauss distribution (normaldistribution) is 2.30.

The light intensity ratio I₁/I₂ is preferably set to 0.40 or more, morepreferably set to 0.50 or more, still more preferably set to 0.60 ormore, and particularly preferably set to 0.70 or more. Further, thelight intensity ratio I₁/I₂ is preferably 2.00 or less, more preferably1.90 or less, still more preferably 1.80 or less, and particularlypreferably 1.70 or less.

In the present invention, the lower limit value of the ratio I₁/I₂ ispreferably 0.40, more preferably 0.50, still more preferably 0.60, andparticularly preferably 0.70. In the present invention, the upper limitof the ratio I₁/I₂ is preferably 2.00, more preferably 1.90, still morepreferably 1.80, and particularly preferably 1.70.

When the ratio I₁/I₂ is more than 2.00, the light intensity at thecenter position of the irradiated laser beam is increased, an excessiveamount of energy is applied to the thermally reversible recordingmedium, and when an image is repeatedly recorded and erased, erasureresidue may occur due to deterioration of the thermally reversiblerecording medium. In the meanwhile, the ratio I₁/I₂ is less than 0.40,irradiation energy is less applied to the center position of theirradiated laser beam than to peripheral portions thereof, when an imageis recorded, the center portion of a line may not be color-developed,and the line may be split into two lines. When the irradiation energy isincreased so that the center portion of the line is color-developed, thelight intensity at the peripheral portions is excessively increased, anexcessive amount of energy is applied to the thermally reversiblerecording medium, and when an image is repeatedly recorded and erased,erasure residue may occur in peripheral portions of the line due todeterioration of the thermally reversible recording medium.

Further, when the ratio I₁/I₂ is greater than 1.59, the lightirradiation intensity at the center position of the laser beam is higherthan the light irradiation intensity at the peripheral portions, andthus, the thickness of image lines can be changed while preventingdeterioration of the thermally reversible recording medium due torepeated image recording and image erasing, without necessity ofchanging the irradiation distance, by controlling the irradiation power.

FIGS. 3B to 3E respectively show one example of a light intensitydistribution curve obtained when a light intensity of the irradiatedlaser beam is changed. FIG. 3B shows a Gauss distribution. In such alight intensity distribution having a highest light irradiationintensity at a center portion thereof, a ratio of I₁/I₂ becomes high (ina Gauss distribution, a ratio of I₁/I₂=2.3). Further, in a lightintensity distribution, as shown in FIG. 3C, having a lower lightirradiation intensity at a center position thereof than in the lightintensity distribution as shown in FIG. 3B, a ratio of I₁/I₂ is lowerthan that in the light intensity distribution as shown in FIG. 3B. In alight intensity distribution having a top-hat shape as shown in FIG. 3D,a ratio of I₁/I₂ is lower than that in the light intensity distributionas shown in FIG. 3C. In a light intensity distribution, as shown in FIG.3E, where the light irradiation intensity at a center position of theirradiated laser beam is low and the light intensity distribution inperipheral portions thereof is high, a ratio of I₁/I₂ is lower than thatin the light intensity distribution as shown in FIG. 3D. Accordingly,the ratio of I₁/I₂ represents a shape of the light intensitydistribution of the laser beam.

When the ratio of I₁/I₂ is 1.59 or less, a top-hat shaped lightintensity distribution or a light intensity distribution where the lightintensity at a center portion thereof is lower than the light intensityin peripheral portions thereof appears.

Here, the “80% light energy bordering surface of the total light energyof the irradiated laser beam” means a surface or a plane marked, forexample, as shown in FIG. 3A, it means a surface or a plane marked whena light intensity of an irradiated laser beam is measured using ahigh-power beam analyzer using a high-sensitive pyroelectric camera, theobtained light intensity is three-dimensionally graphed, and the lightintensity distribution is separated so that 80% of the total lightenergy sandwiched by a horizontal plane to a plane where Z is equal tozero and the plane where Z is equal to zero is contained therebetween.

In the image processing method according to the first embodiment to thethird embodiment of the present invention, a laser emitting the laserbeam is not particularly limited and may be suitably selected from amongthose known in the art. Examples thereof include CO₂ lasers, YAG lasers,fiber lasers, and laser diodes (LDs).

For a measurement method of the light intensity on a cross-section inthe perpendicular direction to the proceeding direction of the laserbeam, when the laser beam is emitted from, for example, a laser diode, aYAG laser or the like and has a wavelength within the near-infraredrange, the light intensity can be measured using a laser beam profilerusing a CCD etc. When the laser beam is emitted from a CO₂ laser and hasa wavelength in the far-infrared range, the CCD cannot be used. Thus,the light intensity can be measured using a combination of a beamsplitter and a power meter, a high-power beam analyzer using ahigh-sensitive pyroelectric camera, or the like.

A method of changing the light intensity distribution of the laser beamof the Gauss distribution such that a light irradiation intensity I₁ ata center portion of the irradiated laser beam and a light irradiationintensity I₂ on an 80% light energy bordering surface to the total lightenergy of the irradiated laser beam satisfy the expression,0.40≦I₁/I₂≦2.00 is not particularly limited and may be suitably selectedin accordance with the intended use. For example, a light irradiationintensity controlling unit can be preferably used.

Preferred examples of the light irradiation intensity controlling unitinclude lenses, filters, masks, mirrors, and fiber-coupling devices,however, the light irradiation intensity controlling unit is not limitedthereto. Of these, lenses are preferable because they have less energyloss. For the lens, a collide scope, an integrator, a beam-homogenizer,an aspheric beam-shaper (a combination of an intensity conversion lensand a phase correction lens), an aspheric device lens, a diffractiveoptical element or the like can be preferably used. In particular,aspheric device lenses and diffractive optical elements are preferable.

When a filter or a mask is used, the light irradiation intensity can becontrolled by physically cutting a center part of the laser beam. When amirror is used, the light irradiation intensity can be controlled byusing a deformable mirror which is capable of mechanically changing theshape of a light beam in conjunction with a computer or a mirror whosereflectance or surface convexoconcaves can be partially changed.

In the case of a laser having an oscillation wavelength of near-infraredlight or visible light, it is preferable to use it because the lightirradiation intensity can be easily controlled by fiber-coupling.

The method of controlling a light irradiation intensity using the lightirradiation intensity controlling unit will be described below in thedescription of the image processor of the present invention.

The output power of a laser beam irradiated in the image recording stepis not particularly limited and may be suitably selected in accordancewith the intended use, however, it is preferably 1 W or more, morepreferably 3 W or more, and still more preferably 5 W or more. Theoutput power of the laser beam is less than 1 W, it takes some time torecord an image, and when the image recording time is intended toshorten, a high-density image cannot be obtained due to an insufficientoutput power. The upper limit of the output power of the laser beam isnot particularly limited and may be suitably selected in accordance withthe intended use, however, it is preferably 200 W or less, morepreferably 150 W or less, and still more preferably 100 W or less. Whenthe output power of the laser beam is more than 200 W, the laser deviceused is possibly increased in size.

The scanning speed of a laser beam irradiated in the image recordingstep is not particularly limited and may be suitably selected inaccordance with the intended use, however, it is preferably 300 mm/s ormore, more preferably 500 mm/s or more, and still more preferably 700mm/s or more. When the scanning speed is less than 300 mm/s or less, ittakes some time to record an image. The upper limit of the scanningspeed of the laser beam is not particularly limited and may be suitablyselected in accordance with the intended use, however, it is preferably15,000 mm/s or less, more preferably 10,000 mm/s or less, and still morepreferably 8,000 mm/s or less. When the scanning speed is more than15,000 mm/s, there may be a difficulty in recording a uniform image.

The spot diameter of a laser beam irradiated in the image recording stepis not particularly limited and may be suitably selected in accordancewith the intended use, however, it is preferably 0.02 mm or more, morepreferably 0.1 mm or more, and still more preferably 0.15 mm/s or more.The upper limit of the spot diameter of the laser beam is notparticularly limited and may be suitably selected in accordance with theintended use, however, it is preferably 3.0 mm or less, more preferably2.5 mm or less, and still more preferably 2.0 mm or less. When the spotdiameter is small, the line width of lines constituting an image becomesthin, the contrast becomes low, resulting in a low visibility. When thespot diameter is large, the line width of lines constituting an imagebecomes thick, adjacent lines are overlapped with each other, resultingin incapability of printing small characters.

The output power of a laser beam irradiated in the image erasing stepwhere a recorded image is erased by irradiating and heating thethermally reversing recording medium with the laser beam is notparticularly limited and may be suitably selected in accordance with theintended use, however, it is preferably 5 W or more, more preferably 7 Wor more, and still more preferably 10 W or more. When the output powerof the laser beam is less than 5 W, it takes some time to erase arecorded image, and when the image erasing time is intended to shorten,an image erasing defect occurs due to an insufficient output power. Theupper limit of the output power of the laser beam is not particularlylimited and may be suitably selected in accordance with the intendeduse, however, it is preferably 200 W or less, more preferably 150 W orless, and still more preferably 100 W or less. When the output power ofthe laser beam is more than 200 W, the laser device used is possiblyincreased in size.

The scanning speed of a laser beam irradiated in the image erasing stepwhere a recorded image is erased by irradiating and heating thethermally reversible recording medium with the laser beam is notparticularly limited and may be suitably selected in accordance with theintended use, however, it is preferably 100 mm/s or more, morepreferably 200 mm/s or more, and still more preferably 300 mm/s or more.When the scanning speed is less than 100 mm/s, it takes some time toerase a recorded image. The upper limit of the scanning speed of thelaser beam is not particularly limited and may be suitably selected inaccordance with the intended use, however, it is preferably 20,000 mm/sor less, more preferably 15,000 mm/s or less, and still more preferably10,000 mm/s or less. When the scanning speed is more than 20,000 mm/s,there may be a difficulty in recording a uniform image.

The spot diameter of a laser beam irradiated in the image erasing stepwhere a recorded image is erased by irradiating and heating thethermally reversible recording medium with the laser beam is notparticularly limited and may be suitably selected in accordance with theintended use, however, it is preferably 0.5 mm or more, more preferably1.0 mm or more, and still more preferably 2.0 mm or more. The upperlimit of the spot diameter of the laser beam is not particularly limitedand may be suitably selected in accordance with the intended use,however, it is preferably 14.0 mm or less, more preferably 10.0 mm orless, and still more preferably 7.0 mm or less. When the spot diameteris small, it takes some time to erase a recorded image. When the spotdiameter is large, an image erasing defect may occur due to aninsufficient output power.

<Mechanism of Image Recording and Image Erasing>

Mechanism of the image recording and image erasing is based on an aspectthat transparency reversibly changes depending on temperature, and anaspect that the color tone reversibly changes depending on temperature.

In the aspect that transparency reversibly changes, the organiclow-molecules contained in the thermally reversible recording medium aredispersed in particulate form in the resin, and the transparencyreversibly changes between a transparent state and a white turbiditystate by effect of heat.

The visibility of change in the transparency is derived from thefollowing phenomena. Specifically, (1) in the case of a transparentstate, since particles of the organic low-molecular material dispersedin a resin base material adhere tightly to the resin base material andno void exists inside the particles, light entering from one sidetransmits to the opposite side, and it appears to be transparent. In themeanwhile, (2) in the case of a white-turbid state, particles of theorganic low-molecular material are formed with a fine crystal of theorganic low-molecular material, voids (spaces) are generated at theinterface of the crystal or at the interface between the particles andthe resin base particles, and light emitting from one side is refractedand scattered on the interface between the void and the crystal or atthe interface between the void and the resin. For this reason, itappears to be white.

FIG. 11A shows one example of the one example of thetemperature-transparency variation curve of a thermally reversiblerecording medium having a thermosensitive recording layer (hereinafter,may be referred to as “recording layer”) in which the organiclow-molecular material is dispersed in the resin.

The recording layer is in a white-turbid and opaque state (A) at anormal temperature of T₀ or less. When the recording layer is heated, itgradually becomes transparent from a temperature T₁. When the recordinglayer is heated at a temperature T₂ to T₃, it becomes transparent (B).Even though the temperature is restored to the normal temperature T₀ orless from this state, the recording layer remains transparent (D). Thiscan be considered as follows. The resin starts to be softened at nearthe temperature T₁, and the resin shrinks as the softening progresses toreduce the voids at the interface between the resin and the organiclow-molecular material particles or inside the particles, therefore, thetransparency is gradually increased. At the temperature T₂ to T₃, theorganic low-molecular material becomes semi-molten, or remaining voidsare filled with the organic low-molecular material and then therecording layer becomes transparent. When the recording layer is cooledin a state where a seed crystal remains thereon, it is crystallized at arelatively high-temperature. Since the resin is still in a softenedstate at this point in time, the resin can follow a change in volume ofthe particles associated with the crystallization, and the transparentstate can be maintained without generating the voids.

When the recording layer is further heated to a temperature T₄ or more,it becomes a semi-transparent state (C) which is an intermediate statebetween the maximum transparency and the maximum opacity. Next, when thetemperature is lowered, the state of the recording layer returns to theinitial state of white-turbid and opaque state (A) without becoming atransparent state. This can be considered as follows. After the organiclow-molecular material is completely dissolved at the temperature T₄ ormore, the organic low-molecular material becomes supercooled, andcrystallized at a temperature slightly higher than the temperature T₀.In the crystallization, the resin cannot follow a change in volume ofthe particles associated with the crystallization, and thus voids aregenerated.

However, in the temperature-transparency variation curve shown in FIG.11A, when the type of the resin, the organic low-molecular material andthe like is changed, the transparency in the respective states may varydepending on the type.

Further, FIG. 11B is a schematic illustration showing a mechanism of achange in transparency of a thermally reversible recording medium thatreversibly changes between a transparent state and a white-turbid stateby effect of heat.

In FIG. 11B, one long-chain low-molecule particle and high-moleculeparticles around the long-chain low-molecule particle are taken, andgeneration of voids and a change in color-erasure associated withheating and cooling are illustrated. In the white-turbid state (A),voids are generated between a high-molecular particle and a low-moleculeparticle (or inside particles), and the recording layer is in alight-scattered state. Then, the recording layer is heated to atemperature higher than the softening point (Ts) of the high-molecule,the number of voids decreases and the transparency increases. When therecording layer is further heated to near the melting point (Tm) of thelow-molecule particle, part of the low-molecule particle is melted, andthe voids are filled with the low-molecule particle because of volumeexpansion of the melted low-molecule particle, the voids disappear, andthe recording layer is in the transparent state (B). When the recordinglayer is cooled from that state, the low-molecule particle iscrystallized at the melting point (Tm) thereof, and the transparentstate (D) is maintained even at room temperature, without generatingvoids.

Next, when the recording layer is heated to a temperature higher thanthe melting point of the low-molecule particle, a difference inrefractive index arises between the melted low-molecule particle and thecircumjacent high-molecules, and the recording layer becomessemi-transparent (semi-transparent state) (C). When the recording layeris cooled to the room temperature, the low-molecule particle shows asupercooling phenomenon, is crystallized at a temperature lower than thesoftening point of the high-molecule. Since the high-molecule is in aglass state at this point in time, the circumjacent high-moleculescannot follow a reduction in volume of the particles associated with thecrystallization of the low-molecule particle, voids are generated, andthe recording layer returns to its original state of the white-turbidstate (A).

For the above-mentioned reasons, even when the organic low-molecularmaterial is heated to an image-erasing temperature before beingcrystallized, the organic low-molecular material is in a molten state,and thus it becomes supercooled. Because the resin cannot follow achange in volume of the particles associated with the crystallization ofthe organic low-molecular material, voids are generated, and thus it isconsidered that the recording layer becomes white-turbid.

Next, in the aspect that color tone reversibly changes depending ontemperature, the unmelted organic low-molecular material is composed ofa leuco dye and a reversible developer (hereinafter, may be referred toas “developer”) that have been dissolved therein; and the uncrystallizedorganic low-molecular material is composed of the leuco dye and thedeveloper, and the color tone reversibly changes between a transparentstate and a color-developed state by effect of heat.

FIG. 12A shows one example of the temperature-color development densityvariation curve of a thermally reversible recording medium having areversible thermosensitive recording layer containing the leuco dye andthe developer in the resin. FIG. 12B shows a color developing-colorerasing mechanism of a thermally reversible recording medium in which atransparent state and a color-developed state is reversible changed byeffect of heat.

First, when the recording layer being originally in a color-erased stateis heated, the leuco dye and the developer are melted and mixed at amelting temperature T₁, the recording layer is color-developed to becomea melt-color-developed state (B). From the melt-color-developed state,the recording layer is quenched, the recording layer can be decreased intemperature in a state where the color-developed state remains. Thecolor-developed state is stabilized and solidified to become a colordeveloped-state (C). Whether or not the color-developed state can beobtained depends on the decreasing temperature rate when measured fromthe molten state. When the recording layer is slowly cooled, the coloris erased in the course of temperature decrease to be in a color-erasedstate (A) same as the original state or in a state where the density isrelatively lower than that in the color-developed-state (C) caused byquenching. In the meanwhile, the recording layer is again increased intemperature from the color-developed state (C), the color is erased(from D to E) at a temperature T₂ lower than the color developmenttemperature, and when the recording layer is decreased in temperaturefrom this state, it returns to the color-erased state (A) that is thesame as the original state.

The color-developed state (C) obtained by quenching the recording layerfrom a molten state is in a state where the leuco dye and the developerare mixed in a state where molecules thereof can contact react with eachother, in which, it is likely to form a solid state. This state is astate where the melt mixture of the leuco dye and the developer (thecolor development mixture) is crystallized to keep the colordevelopment, and it can be considered that the color development isstabilized by the form of the structure. In the meanwhile, the colorerased state is a state where the leuco dye and the developerphase-separate from each other. This state is a state where molecules ofat least one compound aggregate to form a domain or to be crystallized,and can be considered as a stabilized state where the leuco dye and thedeveloper phase-separate from each other by aggregation orcrystallization of the molecules. In many cases, more completecolor-erased state is ensured by a phase separation between the leucodye and the developer and a crystallization of the developer.

Note that in both color-erasure by quenching the recording layer from amolten state and color-erasure by increasing the temperature of therecording layer from a color-developed state shown in FIG. 12A, theaggregation structure is changed at the temperature T₂ to cause a phasechange between the leuco dye and the developer and the crystallizationof the developer.

In view of the above-mentioned, it is considered that when the recordinglayer is heated to an image erasing temperature before the colordevelopment mixture formed of the developer melted in the leuco dye iscrystallized, and a phase separation between the leuco dye and thedeveloper is prevented; as a result, the color-developed state ismaintained.

A method of checking that the organic low-molecular material is meltedand is in a state where it has not yet been crystallized and the methodof measuring time until the melted organic low-molecular material iscrystallized are not particularly limited and may be suitably selectedin accordance with the intended use. For example, a first straight-lineimage is recorded, a given length of time later, a second straight-lineimage is recorded so as to be overlapped in the perpendicular directionto the first straight-line image, and whether or not an intersectingpoint of these straight lines is erased is judged to thereby checkwhether or not the organic low-molecular material is melted but has notyet been crystallized. When the intersecting point is erased, it can berecognized that the organic low-molecular material is crystallized.

The state where the intersecting point is erased means that for example,when the image density of the straight-line image including theintersecting point is continuously measured using a densitometer (RD914,manufactured by Macbeth Co., Ltd.), in an aspect where the transparencyof the thermally reversible recording medium reversible changes, theimage density is 1.2 or more, and in an aspect where the color tone ofthe thermally reversible recording medium reversibly changes, the imagedensity is 0.5 or less. Note that in the aspect where the transparencyof the thermally reversible recording medium reversibly changes, theimage density is measured after setting a black paper sheet (O.D.value=2.0) under the thermally reversible recording medium.

Whether or not the organic low-molecular material is crystallized canalso be checked by subjecting the thermally reversible recording mediumto an X-ray analysis. When the organic low-molecular material iscrystallized, the crystallized organic low-molecular material shows aunique crystal structure depending on the type of the organiclow-molecular material, and a scattered peak corresponding to thecrystal structure can be detected by an X-ray analysis. The position ofthe scattered peak can be easily checked by subjecting the organiclow-molecular material alone to an X-ray analysis. By means of an X-rayanalyzer, the position of the scattered peak can be measured withvarying the temperature, and thus after the organic low-molecularmaterial is heated and melted, the crystallization process of theorganic low-molecular material can be checked.

[Thermally Reversible Recording Medium]

The thermally reversible recording medium used in the image processingmethod of the present invention has at least a substrate and areversible thermosensitive recording layer and further has other layerssuitably selected in accordance with necessity such as a protectivelayer, an intermediate layer, an undercoat layer, a back layer, aphotothermal conversion layer, an adhesive layer, a tacky layer, acolored layer, an air-space layer and a light reflective layer. Each ofthese layers may be formed in a single-layer structure or amulti-layered structure.

—Substrate—

The substrate is not particularly limited as to the shape, structure,size, and the like, and may be suitably selected in accordance with theintended use. For the shape, for example, a planar shape is exemplified.The structure may be a single structure or a multi-layered structure.The size of the substrate can be suitably selected in accordance withthe size of the thermally reversible recording medium.

Examples of material of the substrate include inorganic materials andorganic materials.

Examples of the inorganic materials include glass, quartz, silicons,silicone oxides, aluminum oxides, SiO₂, and metals.

Examples of the organic materials include paper; cellulose derivativessuch as triacetate cellulose; synthetic paper; and films of polyethyleneterephthalate, polycarbonate, polystyrene, and polymethyl methacrylate.

Each of these inorganic materials and organic materials may be usedalone or in combination with two or more. Of these, organic materialsare preferable. Films of polyethylene terephthalate, polycarbonate,polymethyl methacrylate or the like are preferable. Polyethyleneterephthalate is particularly preferable.

It is preferable that the substrate surface be reformed by subjecting toa corona discharge treatment, an oxidation treatment (chromic acid,etc.), an etching treatment, an easy adhesion treatment, or anantistatic treatment for the purpose of improving the adhesion propertyof the coating layer.

Further, the substrate surface can be colored in white by adding a whitepigment such as titanium oxide.

The thickness of the substrate is not particularly limited and may besuitably selected in accordance with the intended use, however, it ispreferably 10 μm to 2,000 μm and more preferably 50 μm to 1,000 μm.

—Reversible Thermosensitive Recording Layer—

The reversible thermosensitive recording layer (hereinafter, may bereferred to as “recording layer” simply) contains at least a materialthat reversibly changes any one of its transparency and color tonedepending on temperature and further contains other components inaccordance with the intended use.

The material that reversibly changes any one of its transparency andcolor tone depending on temperature is a material capable of expressinga phenomenon of reversibly generating a visible change by a change intemperature and is capable of changing between a relativelycolor-developed state and a color-erased state depending on a differencein heating temperature and cooling rate after heating. In this case, thevisible change is classified into a change in color state and a changein shape. The change in color state is attributable to a change, forexample, in transmittance, reflectance, absorption wavelength andscattering level, and the thermally reversible recording mediumvirtually changes in color tone state depending on a combination ofthese changes.

The material that reversibly changes any one of its transparency andcolor tone depending on temperature is not particularly limited and maybe suitably selected from among those known in the art, however, amaterial that reversibly changes any one of its transparency and colortone at between the first specific temperature and the second specifictemperature is particularly preferable in terms that it allows foreasily controlling the temperature and obtaining a high-contrast.

Specific examples thereof include a material that becomes transparent ata first specific temperature and becomes white-turbid at a secondspecific temperature (see Japanese Patent Application Laid-Open (JP-A)No. 55-154198), a material that is color-developed at a second specifictemperature and is color-erased at a first specific temperature (seeJapanese Patent Application Laid-Open (JP-A) Nos. 4-224996, 4-247985,4-267190, etc.), a material that becomes white-turbid at a firstspecific temperature and becomes transparent at a second specifictemperature (see Japanese Patent Application Laid-Open (JP-A) No.3-169590), and a material that is color-developed in black, red, blue orthe like at a first specific temperature and is color-erased at a secondspecific temperature (see Japanese Patent Application Laid-Open (JP-A)Nos. 2-188293, 2-188294, etc.)

Of these, a thermally reversible recording medium containing a resinbase material and an organic low-molecular material such as ahigher-fatty acid which is dispersed in the resin base material isadvantageous in that a second specific temperature and a first specifictemperature are relatively low and images can be recorded and erasedwith low-energy. Further, the color-developing and color-erasingmechanism of such a material is based on a physical change depending onsolidification of the resin and crystallization of the organiclow-molecular material, and thus the material has strong environmentalresistance.

Further, a thermally reversible recording medium using a leuco dye and areversible developer, which will be described hereinafter, iscolor-developed at a second specific temperature and is color-erased ata first specific temperature, reversibly changes between a transparentstate and a color-developed state, and it allows for obtaining ahigh-contrast image because the thermally reversible recording mediumcan be colored in black, blue or other colors in the color-developedstate.

The organic low-molecular material (which is dispersed in a resin basematerial, is in a transparent state at a first specific temperature andis in a white-turbid state at a second specific temperature) used in thethermally reversible recording medium is not particularly limited aslong as it can change from a polycrystal to a single crystal by effectof heat, and may be suitably selected in accordance with the intendeduse. Typically, an organic material having a melting point of around 30°C. to 200° C. can be used, and an organic material having a meltingpoint of 50° C. to 150° C. is preferably used.

Such an organic low-molecular material is not particularly limited andmay be suitably selected in accordance with the intended use. Examplesthereof include alkanol; alkane diol; halogen alkanol or halogen alkanediol; alkyl amine; alkane; alkene; alkyne; halogen alkane; halogenalkene; halogen alkyne; cycloalkane; cycloalkene; cycycloalkyne;unsaturated or saturated mono carboxylic acid or unsaturated orsaturated dicarboxylic acid and esters thereof, and amide or ammoniumsalts thereof; unsaturated or saturated halogen fatty acids and estersthereof, and amide or ammonium salts thereof; aryl carboxylic acids andesters thereof, and amide or ammonium salts thereof; halogen allylcarboxylic acids and esters thereof, and amide or ammonium saltsthereof; thioalcohols; thiocarboxylic acids and esters thereof, andamine or ammonium salts thereof; and carboxylic acid esters ofthioalcohol. Each of these organic low-molecular materials may be usedalone or in combination with two or more.

The number of carbon atoms of these compounds is preferably 10 to 60,more preferably 10 to 38, and particularly preferably 10 to 30. Alcoholbase sites in the esters may be saturated, unsaturated orhalogen-substituted.

Further, the organic low-molecular material preferably contains at leastone selected from oxygen, nitrogen, sulfur and halogen in moleculesthereof, for example, —OH, —COOH, —CONH—, —COOR, —NH—, —NH₂, —S—, —S—S—,—O—, halogen atom, etc.

Specific examples of these compounds include higher fatty acids such aslauric acid, dodecanoic acid, myristic acid, pentadecanoic acid,palmitic acid, stearic acid, behenic acid, nonadecanoic acid, alginicacid, and oleic acid; and higher fatty acid esters such as methylstearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate,and tetradecyl palmitate. Of these, as an organic low-molecular materialused in the third embodiment of the image processing method, a higherfatty acid is preferable, a higher fatty acid having 16 or more carbonatoms such as palmitic acid, stearic acid, behenic acid, and lignocericacid, is more preferable, and a higher fatty acid having 16 to 24 carbonatoms is still more preferable.

To widen the range of temperature at which the thermally reversiblerecording medium can be made transparent, the above-mentioned variousorganic low-molecular materials may be used in combination with eachother suitably, or a combination of the organic low-molecular materialand another material having a different melting point from that of theorganic low-molecular material may be used. These materials aredisclosed, for example, in Japanese Patent Application Laid-Open (JP-A)Nos. 63-39378 and 63-130380 and Japanese Patent (JP-B) No. 2615200,however, are not limited thereto.

The resin base material serves to form a layer in which the organiclow-molecular material is uniformly dispersed and maintained and affectsthe transparency of the thermally reversible recording layer at the timeof obtaining the maximum transparency. Therefore, the resin basematerial is preferably a resin having high-transparency, mechanicalstability and excellent layer-formability.

Such a resin is not particularly limited and may be suitably selected inaccordance with the intended use. Examples thereof include polyvinylchlorides; vinyl chloride copolymers such as vinyl chloride-vinylacetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer,vinyl chloride-vinyl acetate-maleic acid copolymer, and vinylchloride-acrylate copolymer; polyvinylidene chlorides; vinylidenechloride copolymers such as vinylidene chloride-vinyl chloridecopolymers, and vinylidene chloride-acrylonitrile copolymer; polyesters;polyamides, polyacrylate or polymethacrylate or acrylate-methacrylatecopolymers; and silicone resins. Each of these resins may be used aloneor in combination with two or more.

A ratio of the organic low-molecular material to the resin (resin basematerial) in the recording layer, as expressed as a mass ratio, ispreferably about 2:1 to 1:16 and more preferably 1:2 to 1:8.

When the ratio of the resin is smaller than 2:1, there may be caseswhere it is difficult to form a layer in which the organic low-molecularmaterial is held in the resin base material. When the ratio of the resinis greater than 1:16, there may be cases where it is difficult to makethe recording layer opacified.

Besides the organic low-molecular material and the resin, to facilitaterecording of a transplant image, other components such as a high-boilingpoint solvent and a surfactant can be added to the recording layer.

A method of forming the recording layer is not particularly limited andmay be suitably selected in accordance with the intended use. Forexample, a dispersion liquid in which the organic low-molecular materialis dispersed in particulate form in a solution with two components ofthe resin base material and the organic low-molecular material dissolvedtherein or a solution of the resin base material (for the solvent, asolvent in which at least one selected from the organic low-molecularmaterials is insoluble is used) is applied over a surface of thesubstrate, and the substrate surface is dried to thereby a recordinglayer can be formed.

The solvent used for forming the recording layer is not particularlylimited and may be suitably selected in accordance with the type of theresin base material and the organic low-molecular material. For example,tetrahydrofuran, methylethylketone, methylisobutylketone, chloroform,carbon tetrachloride, ethanol, toluene and benzene are exemplified.

In a recording layer formed by using the solution, not to mention arecording layer formed by using the dispersion liquid, the organiclow-molecular material is deposited as a fine particle and exists inparticulate form.

In the thermally reversible recording medium, the organic low-molecularmaterial may be a material that is composed of the leuco dye and thereversible developer, develops color at a second specific temperatureand erases color at a first specific temperature. The leuco dye is acolorless or pale color dye precursor itself. The leuco dye is notparticularly limited and may be suitably selected from among those knownin the art. Preferred examples thereof include leuco compounds such astriphenyl methane phthalide leuco compounds, triallyl methane leucocompounds, fluoran leuco compounds, phenothiazine leuco compounds,thiofluoran leuco compounds, xanthene leuco compounds, indophthalylleuco compounds, spiropyran leuco compounds, azaphthalide leucocompounds, couromeno-pyrazole leuco compounds, methine leuco compounds,rhodamineanilinolactam leuco compounds, rhodaminelactam leuco compounds,quinazoline leuco compounds, diazaxanthene leuco compounds, andbislactone leuco compounds. Of these, fluoran leuco dyes and phthalideleuco dyes are particularly preferable in terms that they are excellentin color developing-color erasing property, hue, storage stability andthe like. Each of these dyes may be sued alone or in combination withtwo or more. Further, by forming a layer that develops different colortones in a multi-layered structure, it is possible to use the layer inmulti-color image formation or in full-color image formation.

The reversible developer is not particularly limited as long as it canreversibly develop and erase color by utilizing heat as a factor, andmay be suitably selected in accordance with the intended use. Preferredexamples of the reversible developer include a compound having, inmolecules thereof, one or more structures selected from (1) a structurehaving color developability for developing color of the leuco dye (forexample, phenolic hydroxyl group, carboxylic group, phosphoric group,etc.) and (2) a structure of controlling cohesive attraction betweenmolecules (for example, a structure in which a long-chain hydrocarbongroup is bonded). In the bonded site, the long-chain hydrocarbon groupmay be bonded via a divalent or more bond group containing a heteroatom. Further, in the long-chain hydrocarbon group, at least any of thesame bond group and an aromatic group may be contained.

For the (1) structure having color developability for developing colorof leuco dye, phenol is preferable.

For the (2) structure of controlling cohesive attraction betweenmolecules, a long-chain hydrocarbon group having 8 or more carbon atomsis preferable. The number of carbon atoms is more preferably 11 or more,and the upper limit of the number of carbon atoms is preferably 40 orless and more preferably 30 or less.

Among the reversible developers, a phenol compound represented by thefollowing General Formula (1) is preferable, and a phenol compoundrepresented by the following General Formula (2) is more preferable.

In General Formulas (1) and (2), “R¹” represents a single bond aliphatichydrocarbon group or a fatty acid hydrocarbon group having 1 to 24carbon atoms; “R²” represents an aliphatic hydrocarbon group having 2 ormore carbon atoms that may have a substituent group, the number ofcarbon atoms is preferably 5 or more and more preferably 10 or more; and“R³” represents an aliphatic hydrocarbon group having 1 to 35 carbonatoms, and the number of carbon atoms is preferably 6 to 35 and morepreferably 8 to 35. Each of these aliphatic hydrocarbon groups may existsingularly or two or more selected therefrom may be combined.

The sum of the number of carbon atoms in the R¹, R², and R³ is notparticularly limited and may be suitably selected in accordance with theintended use, however, the lower limit of the sum is preferably 8 ormore and more preferably 11 or more. The upper limit of the sum ispreferably 40 or less and more preferably 35 or less.

When the sum of the number of carbon atoms is less than 8, the stabilityof color development and color erasing ability may degrade.

The aliphatic hydrocarbon group may be a straight chain or branchedchain or may have an unsaturated bond, however, it is preferably astraight chain. Examples of the substituent group bonded to thehydrocarbon group include hydroxyl group, halogen atom, and alkoxygroup.

“X” and “Y” may be the same to each other or different from each other,respectively represent a divalent group containing an N atom or an Oatom. Specific examples thereof include oxygen atom, amide group, ureagroup, diacylhydrazine group, diamide-oxalate group, and acyl-ureagroup. Of these, amide group and urea group are preferable.

Further, “n” is an integer of 0 to 1.

For the reversible developer, it is preferable to use a compound havingat least one of —NHCO— group and —OCONH— group be used in combination inmolecules thereof as a color-erasing accelerator. In this case, in thecourse of forming a color-erased state, an inter-molecular interactionis induced between the color-erasing accelerator and the reversibledeveloper, and the color developing-color erasing property is improved.

A mixing ratio between the leuco dye and the reversible developer cannotbe unequivocally defined because the appropriate range varies dependingon a combination of compounds to be used, however, generally, asexpressed as a mole ratio, the mixing ratio of the reversible developerto the leuco dye is preferably 0.1 to 20 to 1 mole of the leuco dye andmore preferably 0.2 moles to 10 moles to 1 mole of the leuco dye.

When the mixing ratio of the reversible developer is less than 0.1, or20 or more, the color-developed density in the color-developed state maybe reduced.

When the color-erasing accelerator is added, the additive amount thereofis preferably 0.1 parts by mass to 300 parts by mass and more preferably3 parts by mass to 100 parts by mass to 100 parts by mass of thereversible developer.

Note that the leuco dye and the reversible developer may also becapsulated in a micro capsule for use.

When the organic low-molecular material is composed of the leuco dye andthe reversible developer, the thermally reversible thermosensitiverecording layer contains, besides these components, a binder resin and acrosslinker and further contains other components in accordance withnecessity.

The binder resin is not particularly limited as long as it can bind therecording layer on the substrate, and it is possible to mix at least onesuitably selected from conventional resins for use.

For the binder resin, to improve the durability in repetitive use, aresin that is curable by heat, ultraviolet ray, electron beam or thelike is preferable, and a thermosetting resin using an isocyanatecompound as a crosslinker is particularly preferable.

Examples of the thermosetting resin include a resin having a groupcapable of reacting to a crosslinker such as hydroxy group and carboxylgroup; and a resin copolymerized between a monomer having a hydroxylgroup, a carboxyl group or the like and another monomer.

Such a thermosetting resin is not particularly limited and may besuitably selected in accordance with the intended use. Examples thereofinclude phenoxy resins, polyvinyl butyral resins, cellulose acetatepropionate resins, cellulose acetate butylate resins, acrylpolyolresins, polyester polyol resins, and polyurethane polyol resins. Each ofthese thermosetting resins may be used alone or in combination with twoor more. Of these, acrylpolyol resins, polyester polyol resins,polyurethane polyol resins are particularly preferable.

A mixing ratio (mass ratio) of the binder resin to the leuco dye in therecording layer is preferably 0.1 to 10 to 1 of the leuco dye. When themixing ratio of the binder resin is less than 0.1, the heat strength ofthe recording layer may be sometimes insufficient, and when more than10, color-developed density may degrade.

The crosslinker is not particularly limited and may be suitably selectedin accordance with the intended use. Examples thereof includeisocyanates, amino resins, phenol resins, amines, and epoxy compounds.Of these, isocyanates are preferable, and a polyisocyanate compoundhaving a plurality of isocyanate groups is particularly preferable.

The additive amount of the crosslinker to the binder resin, at a ratioof the number of functional groups of the crosslinker to the number ofactive groups contained in the binder resin, is preferably 0.01 to 2.When the ratio of the functional group is less than 0.01, the heatstrength may be sometimes insufficient, and when more than 2, it mayadversely affect the color developing-color erasing property.

Further, as a crosslinking accelerator, a catalyst that is generallyused in this type of reaction may be used.

Examples of the crosslinking accelerator include tertiary amines such as1,4-diazabicyclo [2,2,2] octane; and metal compounds such as organic tincompounds.

The gel percent of the thermosetting resin when heat-crosslinked ispreferably 30% or more, more preferably 50% or more, and still morepreferably 70% or more. When the gel percent is less than 30%, thedurability may degrade due to an insufficient crosslinked state.

As a method of distinguishing whether the binder resin is in acrosslinked state or in a non-crosslinked state, it can be distinguishedby immersing the coated layer in a solvent having high solubility. Abinder resin being in a non-crosslinked state will be eluted into thesolvent and will not remain in the solute.

For other components to be added to the recording layer, variousadditives for improving and controlling coating property andcolor-erasing property are exemplified. Examples of these additivesinclude surfactants, plasticizers, conductive agents, fillers,antioxidants, light stabilizers, color-development stabilizers, andcolor-erasing accelerators.

A method of preparing the recording layer is not particularly limitedand may be suitably selected in accordance with the intended use.Preferred examples of the method include (1) a method of which arecording layer coating solution with the binder resin, the leuco dyeand the reversible developer dissolved or dispersed in a solvent isapplied over a surface of the substrate, the solvent is evaporated fromthe solution to form a sheet on the substrate, and the applied coatingsolution is subjected to a crosslinking reaction at the same time orafter the formation of the sheet; (2) a method of which a recordinglayer coating solution with the leuco dye and the reversible developerare dispersed in a solvent that is prepared by dissolving only thebinder resin therein is applied over a surface of the substrate, thesolvent is evaporated from the solution to form a sheet on thesubstrate, and the applied coating solution is subjected to acrosslinking reaction at the same time or after the formation of thesheet; and a method of which the binder resin, the leuco dye and thereversible developer are heated and melted so as to be mixed withoutusing a solvent, the melted mixture is formed in a sheet, the sheet iscooled and then the cooled sheet is subjected to a crosslinkingreaction.

In these methods, it is also possible to form a sheet-shaped thermallyreversible recording medium without using the substrate. The recordinglayer coating solution may be prepared by dispersing various materialsin a solvent using a dispersing device. Each of the materials may besingularly dispersed in a solvent to then be mixed therein, or materialsmay be heated and dissolved, thereafter the dissolved solution may bequenched or slowly cooled to thereby be deposited.

A solvent to be used in the methods of preparing a recording layer (1)or (2) is not particularly limited and may be suitably selected inaccordance with the intended use, however, it varies depending on thetype of the leuco dye and the reversible developer and cannot be definedunequivocally. Examples thereof include tetrahydrofuran,methylethylketone, methylisobutylketone, chloroform, carbontetrachloride, ethanol, toluene, and benzene.

Note that the reversible developer exists in the recording layer in astate of being dispersed in particulate form.

To the recording layer coating solution, for the purpose of expressinghigh-performance as a coating material, various pigments, antifoamingagent, dispersing agent, slipping agent, antiseptic agent, crosslinker,plasticizer and the like may be added.

The coating method of the recording layer is not particularly limitedand may be suitably selected in accordance with the intended use. Asubstrate may be conveyed in a roll in a continuous manner or asubstrate cut in a sheet form may be conveyed, and the recording layercoating solution may be applied over a surface of the substrate, forexample, by a conventional coating method such as blade coating,wire-bar coating, spray-coating, air-knife coating, bead coating,curtain coating, gravure coating, kiss coating, reverse-roller coating,dip coating, and die coating.

The drying conditions of the recording layer coating solution are notparticularly limited and may be suitably selected in accordance with theintended use. For example, the applied recording layer coating solutionmay be dried at a temperature ranging from room temperature to 140° C.for 10 seconds to 10 minutes.

The thickness of the recording layer is not particularly limited and maybe suitably adjusted in accordance with the intended use. For example,it is preferably 1 μm to 20 μm and more preferably 3 μm to 15 μm.

When the thickness of the recording layer is less than 1 μm, imagecontrast may be lowered because the color development density islowered, and when more than 20 μm, the heat distribution inside layersbecomes wide and portions that cannot develop color arise because thetemperature falls below the color developing temperature, and a desiredcolor development density may not be obtained.

—Protective Layer—

The protective layer is preferably formed on the recording layer for thepurpose of protecting the recording layer.

The protective layer is not particularly limited and may be suitablyselected in accordance with the intended use. For example, theprotective layer may be formed into a plurality of layers, however, itis preferably formed as the outermost surface of an exposed layer.

The protective layer contains at least a binder resin and furthercontains other components such as filler, lubricant and color pigmentsin accordance with necessity.

The binder resin used in the protective layer is not particularlylimited and may be suitably selected in accordance with the intendeduse, however, ultraviolet (UV) curable resins, thermosetting resins,electron beam curable resins are preferably exemplified. Of these,ultraviolet (UV) curable resins and thermosetting resins areparticularly preferable.

Since a UV curable resin enables forming an extremely hard film aftercuring thereof and preventing deformation of a recording medium causedby damage of the surface via physical contact and heat from a usedlaser, with use of a UV curable resin, it is possible to obtain athermally reversible recording medium that is excellent in repetitivedurability.

A thermosetting resin also enables forming an extremely hard film,similarly to the case of using UV curable resin, although it is lesscurable than UV curable resin. Thus, with use of a thermosetting resinfor the protective layer, a thermally reversible recording medium thatis excellent in repetitive durability can be obtained.

The UV curable resin is not particularly limited and may be suitablyselected from among those known in the art in accordance with theintended use. Examples thereof include urethane acrylate oligomers,epoxy acrylate oligomers, polyester acrylate oligomers, polyetheracrylate oligomers, vinyl oligomers, and unsaturated polyesteroligomers; various monofunctional or polyfunctional acrylates,methacrylates, vinyl esters, ethylene derivatives, and monomers of allylcompounds. Of these, tetrafunctional or more polyfunctional monomers oroligomers are particularly preferable. By mixing two or more selectedfrom these monomers and oligomers, the hardness of a resin layer,shrinkage, flexibility, strength of the coated layer can be suitablycontrolled.

To cure the monomer or the oligomer using an ultraviolet ray, it ispreferable to use a photopolymerization initiator and aphotopolymerization accelerator.

The additive amount of the photopolymerization initiator and thephotopolymerization accelerator is not particularly limited and may besuitably selected in accordance with the intended use, however, it ispreferably 0.1% by mass to 20% by mass and more preferably 1% by mass to10% by mass to the total mass of resin components used in the protectivelayer.

The ultraviolet curable resin can be irradiated to harden itself with anultraviolet ray using a conventional ultraviolet irradiation device. Forexample, an ultraviolet irradiation device equipped with a light source,lamp fitting, a power source, a cooling apparatus, a conveyer isexemplified.

Examples of the light source include mercury lamps, metal halide lamps,potassium lamps, mercury xenon lamps, and flash lamps.

The wavelength of light emitted from the light source is notparticularly limited and may be suitably selected in accordance with theultraviolet ray absorptive wavelength of the photopolymerizationinitiator and the photopolymerization accelerator contained in therecording layer.

Irradiation conditions of the ultraviolet ray are not particularlylimited and may be suitably selected in accordance with the intendeduse. The lamp output power, conveying speed and the like may be suitablydetermined in accordance with the irradiation energy required tocross-link the resin.

In order to ensure excellent conveyability, it is possible to add areleasing agent such as silicone having a polymerizable group,silicone-grafted polymer, wax, and zinc stearate; and a lubricant suchas silicone oil.

The additive amount of the releasing agent and the lubricant ispreferably 0.01% by mass to 50% by mass and more preferably 0.1% by massto 40% by mass.

Even when the lubricant and the releasing agent are added in a slightamount, the effect can be exerted, however, when the additive amount isless than 0.01% by mass, there may be cases where an effect obtained bythe addition may be hardly exerted, and when more than 50% by mass, itmay cause a problem with adhesion property between the protective layerand a layer formed under the protective layer.

Further, an organic ultraviolet absorbent may be contained in theprotective layer. The content of the organic ultraviolet absorbent ispreferably 0.5% by mass to 10% by mass to the total mass of resincomponents in the protective layer.

To further improve the conveyability, an inorganic filler, an organicfiller and the like may be added to the protective layer. Examples ofthe inorganic filler include calcium carbonate, kaolin, silica, aluminumhydroxide, alumina, aluminum silicate, magnesium hydroxide, titaniumoxide, zinc oxide, barium sulfate, and talc. Each of these inorganicfillers may be used alone or in combination with two or more.

Further, a conductive filler is preferably used as a measure againststatic electricity. For the conductive filler, it is more preferable touse a conductive filler of a needle shape.

For the conductive filler, a titanium oxide whose surface is coated withantimony-doped tin oxide is particularly preferably exemplified.

The particle diameter of the inorganic filler is preferably 0.01 μm to10.0 μm and more preferably 0.05 μm to 8.0 μm.

The additive amount of the inorganic filler is preferably 0.001 parts bymass to 2 parts by mass and more preferably 0.005 parts by mass to 1part by mass to 1 part by mass of the binder resin contained in theprotective layer.

The organic filler is not particularly limited and may be suitablyselected in accordance with the intended use. Examples thereof includesilicone resins, cellulose resins, epoxy resins, nylon resins, phenolresins, polyurethane resins, urea resins, melamine resins, polyesterresins, polycarbonate resins, styrene resins, acryl resins, polyethyleneresins, formaldehyde resins, and polymethyl methacrylate resins.

The thermosetting resin is preferably cross-linked. Thus, for thethermosetting resin, a thermosetting resin having a group capable ofreacting to a curing agent, for example, hydroxy group, amino group, andcarboxyl group, is preferable. A polymer having a hydroxyl group isparticularly preferable.

The improve the strength of the protective layer, the hydroxyl groupvalue of the thermosetting resin is preferably 10 mgKOH/g or more, morepreferably 30 mgKOH/g or more, and still more preferably 40 mgKOH/g ormore in terms that a sufficient coat layer strength can be obtained. Bygiving a sufficient coat layer strength to the protective layer,deterioration of the thermally reversible recording medium can beprevented even when an image is repeatedly erased and recorded. For thecuring agent, for example, the same curing agent used in the recordinglayer can be suitably used.

To the protective layer, conventionally known surfactants, levelingagents, antistatic agents and the like may be added.

Further, a polymer having an ultraviolet absorbing structure(hereinafter, may be referred to as “ultraviolet absorptive polymer”)may also be used.

Here, the polymer having an ultraviolet absorbing structure means apolymer having an ultraviolet absorbing structure (for example,ultraviolet absorptive group) in molecules thereof.

Examples of the ultraviolet absorbing structure include salicylatestructure, cyanoacrylate structure, benzotriazole structure, andbenzophenone structure. Of these, benzotriazole structure andbenzophenone structure are particularly preferable in terms of itsexcellence in light resistance.

The polymer having an ultraviolet absorbing structure is notparticularly limited and may be suitably selected in accordance with theintended use. Examples thereof include copolymers composed of2-(2′-hydroxy-5′-methacryloxyethylphenyl)-2H-benzotriazole,2-hydroxyethyl methacrylate and styrene, copolymers composed of2-(2′-hydroxy-5′-methylphenyl) benzotriazole, 2-hydroxypropylmethacrylate and methyl methacrylate, copolymers composed of2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2-hydroxyethyl methacrylate, methyl methacrylate and t-butylmethacrylate, and copolymers composed of2,2,4,4-tetrahydroxybenzophenone, 2-hydroxypropyl methacrylate, styrene,methyl methacrylate and propyl methacrylate. Each of these polymers maybe used alone or in combination with two or more.

For a solvent used for a coating solution of the protective layer, adispersion device for coating solution, a coating method of theprotective layer, and a drying method, those known methods explained inpreparation of the recording layer can be used. When the ultravioletcurable resin is used, after applying the coating solution and dryingthe applied coating solution, it is necessary to cure the dried surfaceby ultraviolet irradiation. The ultraviolet ray irradiation device,light source, irradiation conditions and the like are as describedhereinabove.

The thickness of the protective layer is not particularly limited andmay be suitably selected in accordance with the intended use, however,it is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 10 μm, andstill more preferably 1.5 μm to 6 μm. When the thickness of theprotective layer is less than 0.1 μm, a function as a protective layerof the thermally reversible recording medium cannot be sufficientlyexerted, the thermally reversible recording medium deteriorates soon dueto repeated heat history and may not be repeatedly used. When thethickness is more than 20 μm, a sufficient amount of heat cannot betransmitted to the recording layer that is formed under the protectivelayer, and an image may not be sufficiently thermally recorded anderased.

—Intermediate Layer—

The intermediate layer is preferably formed in between the recordinglayer and the protective layer for the purpose of improving adhesionproperty therebetween, preventing transformation of the recording layercaused by forming the protective layer, and preventing migration ofadditives contained in the protective layer toward the recording layer.In this case, storage stability of color-developed images can beenhanced.

The protective layer contains at least a binder resin and furthercontains other components such as filler, lubricant and color pigmentsin accordance with necessity.

The binder resin to be used in the intermediate layer is notparticularly limited and may be suitably selected in accordance with theintended use, and resin components such as the binder resins,thermoplastic resins, and thermosetting resins can be used.

Examples of the binder resin include polyethylene resins, polypropyleneresins, polystyrene resins, polyvinyl alcohol resins, polyvinyl butyralresins, polyurethane resins, saturated polyester resins, unsaturatedpolyester resins, epoxy resins, phenol resins, polyearbonate resins andpolyamide resins.

Further, it is preferable that an ultraviolet absorbent be contained inthe intermediate layer. The ultraviolet absorbent is not particularlylimited and may be suitably selected in accordance with the intendeduse. For example, both organic compounds and inorganic compounds can beused.

Note that the organic and inorganic ultraviolet absorbents may becontained in the recording layer.

Further, an ultraviolet absorbing polymer may also be used in theintermediate layer, and the ultraviolet absorbing polymer may be curedusing a crosslinker. For the ultraviolet absorbing polymer and thecrosslinker, the same ones as used for the protective layer can bepreferably used.

The thickness of the intermediate layer is not particularly limited andmay be suitably adjusted in accordance with the intended use, however,it is preferably 0.1 μm to 20 μm and more preferably 0.5 μm to 5 μm.

For a solvent used in a coating solution for the intermediate layer, adispersing device for the coating solution, a coating method of theintermediate layer, a drying method and curing method of theintermediate layer, conventionally known methods that are described inthe preparation of the recording layer can be used.

—Under Layer—

To efficiently utilize applied heat and make the recording medium have ahigh-sensitivity, or for the purpose of improving adhesion propertybetween the substrate and the recording layer and preventinginfiltration of the recording layer materials into the substrate, anunder layer may be formed in between the recording layer and thesubstrate.

The under layer contains at least a hollow particle and further containsother components in accordance with necessity.

Examples of the hollow particle include a single hollow particle inwhich one void is present in one particle, and a multi-hollow particlein which a number of voids are present in one particle. Each of thesehollow particles may be used alone or in combination with two or more.

Material of the hollow particle is not particularly limited and may besuitably selected in accordance with the intended use. For example,thermoplastic resins are preferably exemplified.

The hollow particle may be suitably produced or may be a commerciallyavailable product.

The additive amount of the hollow particle in the under layer is notparticularly limited and may be suitably selected in accordance with theintended use, however, it is preferably 10% by mass to 80% by mass.

For the binder resin to be used in the under layer, the same resins usedin the recording layer or the layer containing a polymer having anultraviolet absorbing structure can be used.

Further, to the under layer, it is possible to add at least one selectedfrom inorganic fillers such as calcium carbonate, magnesium carbonate,titanium oxide, silicon oxide, aluminum hydroxide, kaolin, and talc; andvarious fillers.

To the under layer, other components such as lubricant, surfactant, anddispersing agent can be added.

The thickness of the under layer is not particularly limited and may besuitably adjusted in accordance with the intended use, however, it ispreferably 0.1 μm to 50 μm, more preferably 2 μm to 30 μm, and stillmore preferably 12 μm to 24 μm.

—Back Layer—

To prevent static charge build up and curling of the thermallyreversible recording medium and to improve conveyability thereof, a backlayer may be formed on the opposite surface from a substrate surface onwhich the recording layer is formed.

The back layer contains at least a binder resin and further containsother components such as filler, conductive filler, lubricant, and colorpigments in accordance with necessity.

The binder resin to be used for the back layer is not particularlylimited and may be suitably selected in accordance with the intendeduse. Examples thereof include thermosetting resins, ultraviolet (UV)curable resins, and electron beam curable resins. Of these, ultraviolet(UV) curable resins and thermosetting resins are particularly limited.

For the ultraviolet curable resin and the thermosetting resin to be usedin the back layer, those used in the recording layer, the protectivelayer and the intermediate layer can be preferably used. The sameapplies to the filler, the conductive filler, and the lubricant.

—Photothermal Conversion Layer—

The photothermal conversion layer is a layer having a function to absorblaser beams and generate heat and contains at least a photothermalconversion material having a function to absorb laser beams and generateheat.

The photothermal material is broadly classified into inorganic materialsand organic materials.

Examples of the inorganic materials include carbon black, metals such asGe, Bi, In, Te, Se, and Cr, or semi-metals thereof or alloys thereof.Each of these inorganic materials is formed into a layer form by vacuumevaporation method or by bonding a particulate material to a layersurface using a resin or the like.

For the organic material, various dyes can be suitably used inaccordance with the wavelength of light to be absorbed, however, when alaser diode is used as a light source, a near-infrared absorptionpigment having an absorption peak near wavelengths of 700 nm to 1,500nm. Specific examples of such a near-infrared absorption pigment includecyanine pigments, quinoline pigments, quinoline derivatives ofindonaphthol, phenylene diamine-based nickel complexes, phthalocyaninepigments, and naphthalocyanine pigments. To repeatedly record and erasean image, it is preferable to select a photothermal material that isexcellent in heat resistance.

Each of the near-infrared absorption pigments may be used alone or incombination with two or more. The near-infrared absorption pigment maybe mixed in the recording layer. In this case, the recording layer alsoserves as the photothermal conversion layer.

When the photothermal conversion layer is formed, the photothermalconversion material is typically used in combination with a resin. Theresin used in the photothermal conversion layer is not particularlylimited and may be suitably selected from among those known in the art,as long as it can maintain the inorganic material and the organicmaterial therein, however, thermoplastic resins and thermosetting resinsare preferable.

—Adhesive Layer and Tacky Layer—

The thermally reversible recording medium can be obtained in a form of athermally reversible recording label by forming an adhesive layer or atacky layer on the opposite surface of the substrate from the surfacewith the recording layer formed thereon.

Materials used for the adhesive layer and the tacky layer are notparticularly limited and may be suitably selected from generally usedmaterials in accordance with the intended use.

The materials of the adhesive layer and the tacky layer may be hot melttype materials. Further, peel-off paper or non-peel-off type paper maybe used. By forming the adhesive layer or the tacky layer as describedabove, the recording layer can be affixed on the entire surface or partof a surface of a thick substrate such as a vinyl chloride card providedwith magnetic stripe over which the recording layer is hardly coated.With this treatment, convenience of the thermally reversible recordingmedium can be boosted, for example, part of information stored in amagnetism can be displayed.

Such a thermally reversible recording label with an adhesive layer or atacky layer formed of a surface thereof is suitably used as a thick cardsuch as IC card and optical card.

—Colored Layer—

In the thermally reversible recording medium, a colored layer may beformed in between the substrate and the recording layer for the purposeof improving visibility.

The colored layer can be formed by applying a solution or a dispersionliquid containing a colorant and a resin binder over an intended surfaceand dying the applied solution or dispersion liquid, or by affixing acolor sheet to an intended surface, simply.

Instead of the colored layer, a color print layer may be formed.Examples of a colorant used in the color print layer include variousdyes and pigments contained in color inks used in conventionalfull-color prints.

Examples of the resin binder include various resins such asthermoplastic resins, thermosetting resins, ultraviolet curable resinsor electron beam curable resins.

The thickness of the color print layer is not particularly limited andmay be suitably selected in accordance with a desired print colordensity, because the thickness is suitably changed in accordance with anintended print color density.

In the thermally reversible recording medium, a non-reversible recordinglayer may be used in combination with the reversible recording layer. Inthis case, the color development tones of the respective recordinglayers may be same to each other or different from each other.

Further, a colored layer with a picture or design arbitrarily formed ona surface thereof by printing method such as offset printing and gravureprinting or an inkjet printer, a thermal transfer printer, a sublimationprinter or the like may be formed on part of the same surface as therecording layer of the thermally reversible recording medium, or theentire surface thereof or part of the opposite surface therefrom.Further, on part of the colored layer or the entire surface thereof, anOP varnish layer containing primarily a curable resin may be formed.

For the picture of design, for example, characters, patterns, drawingdesigns, photographs, and information detected with use of an infraredray.

Further, dyes and pigments can also be simply added to any of individuallayers constituting the colored layer to color the layers.

Further, a hologram may be formed on the thermally reversible recordingmedium for security purpose. Furthermore, for giving designing propertyto the thermally reversible recording medium, a design such as portrait,corporate symbol and symbol mark can also be formed by formingconvexoconcaves or irregularities in relief form.

—Shape and Use Application of Thermally Reversible Recording Medium—

The thermally reversible recording medium can be processed in a desiredshape in accordance with use application. For example, it can beprocessed in a card shape, a tag shape, a label shape, a roll shape etc.

A thermally reversible recording medium formed in a card shape can beutilized for prepaid card, point card, credit card, and the like.

A thermally reversible recording medium formed in a tag shape which issmaller in size than card size can be utilized for price tag, and athermally reversible recording medium formed in a tag shape which islarger in size than card size can be used for process management,shipping instructions, tickets and the like.

Since a thermally reversible recording medium formed in a label can beaffixed to other substances, it can be formed in various sizes and usedin process management, article management and the like by affixing it towagons, containers, boxes, containers and the like, which will berepeatedly used. Further, a thermally reversible recording medium formedin a sheet which is larger in size than card size can be used forgeneral documents, process management instructions and the like becauseof its wide area to be recorded.

—Combination Example of Thermally Reversible Recording Component andRF-ID—

In the thermally reversible recording component, the reversiblethermosensitive recording layer (recording layer) that can reversiblydisplay information and an information storage device are formed in onesame card or tag (are integrated into one unit), and part of storedinformation in the information storage device can be displayed on therecording layer. Therefore, the thermally reversible recording componentis extremely convenient and allows for checking information by taking alook at a card or a tag without necessity of preparing a special device.When the contents in the information storage device are rewritten, thethermally reversible recording medium can be repeatedly used byrewriting display data of the thermally reversible recording region.

The information storage device is not particularly limited and may besuitably selected in accordance with the intended use. Preferredexamples thereof include magnetic recording layer, magnetic stripe, ICmemory, optical memory and RF-ID tag. When the information storagedevice is used in process management, article management or the like,RF-ID tag can be particularly preferably used.

The RF-ID tag is composed of an IC chip, and an antenna connected to theIC chip.

The thermally reversible recording component has the recording layerthat can reversibly display information and the information storagedevice. For a preferred example of the information storage device, RF-IDtags are exemplified.

FIG. 13 is a schematic illustration showing one example of an RF-ID tag.An RF-ID tag 85 is composed of an IC chip 81 and an antenna 82 connectedto the IC chip 81. The IC chip 81 is sectioned into four sections of astorage unit, a power source controlling unit, a transmitting unit, anda receiving unit, and each of these units takes partial charge offunctions to transmit information. An antenna between the RF-ID tag 85and a reader/writer communicates information via radio waves to therebyexchange data. Specifically, there are two types of electromagneticinduction method and radio wave method. In the electromagnetic inductionmethod, the antenna 82 in the RF-ID tag 85 receives radio waves, and anelectromotive force is generated by electromagnetic induction, causingparallel resonance. In the radio wave method, the IC chip is activatedby a radiation electromagnetic field. In both of the methods, the ICchip 81 in the RF-ID tag 85 is activated by an external electromagneticfield, information in the chip is converted to signals, and then thesignals are sent out from the RF-ID tag 85. The information is receivedby the antenna provided at the reader/writer and identified by a dataprocessing unit, and the data is processed by software.

The RF-ID tag is formed in a label or card form and can be affixed tothe thermally reversible recording medium. The RF-ID tag can be affixedto the surface of the recording medium with a recording layer formedthereon or the surface of the recording medium with a back layer formedthereon, however, it is preferably affixed to the back layer-formedsurface.

To bond the RF-ID tag to the thermally reversible recording medium, aknown adhesive or a pressure sensitive adhesive can be used.

Further, the thermally reversible recording medium and the RF-ID tag maybe formed by lamination to be integrated into a card form or a tag form.

Hereinafter, one example of the way to use the thermally reversiblerecording component prepared by combining the thermally reversiblerecording medium with the RF-ID tag in process management will bedescribed.

In a process line in which a container containing a delivered rawmaterial is conveyed, a writing unit configured to write a visible imagein a display in non-contact manner while being conveyed, and an erasingunit configured to erase a written image are provided, and further, areader/writer is provided which is configured to read information in anRF-ID attached to the container by a transmitted electromagnetic waveand to rewrite the information in non-contact manner. Further, in theprocess line, a controlling unit is provided which is configured toautomatically diverging, weighing, controlling materials in a physicaldistribution system by utilizing individual information units that areread in non-contact manner while the container being conveyed.

In the RF-ID-attached thermally reversible recording medium affixed tothe container, information on an article name, numerical quantity etc.is recorded on the thermally reversible recording medium and the RF-IDtag, and inspection is performed. In the subsequent process, a processinstruction is given to the delivered raw material, and the informationof the process instruction is recorded on the thermally reversiblerecording medium and the RF-ID tag to prepare a process instruction, andthe process instruction is sent to a processing process. Next, for aprocessed product, order information is recorded as an order instructionon the thermally reversible recording medium and the RF-ID tag. Shippinginformation is read from a container collected after shipment of theproduct, and the container and the RF-ID-attached thermally reversiblerecording medium are to be reused as a container for delivery ofmaterials and an RF-ID-attached thermally reversible recording medium.

Since information is recorded on the thermally reversible recordingmedium in non-contact manner using a laser, the information can berecorded and erased without peeling off the thermally reversiblerecording medium from a container or the like, and further, informationcan be recorded on the RF-ID tag in non-contact manner, the process canbe controlled in real time, and the information stored in the RF-ID tagcan be concurrently displayed on the thermally reversible recordingmedium.

(Image Processor)

The image processor of the present invention is used in the imageprocessing method of the present invention, and has at least a laserbeam emitting unit and a laser light irradiation intensity controllingunit and further has other components suitably selected in accordancewith necessity.

—Laser Beam Emitting Unit—

The laser beam is emitted from a laser oscillator serving as the laserbeam emitting unit. The laser beam emitting unit is not particularlylimited and may be suitably selected in accordance with the intendeduse. For example, commonly used lasers such as CO₂ lasers, YAG lasers,fiber lasers, laser diodes (LDs) are exemplified.

The laser oscillator is needed to obtain a laser beam having ahigh-light intensity and high-directivity. For example, a mirror islocated at both sides of a laser medium, the laser medium is pumped tosupply energy, the number of atoms in an excited state is increased toform an inverted distribution and excite induced emission. Then, onlylight beams in the optical axis direction are selectively amplified, andthe directivity of the light beams is increased, thereby a laser beam isemitted from the output mirror.

The wavelength of a laser beam emitted from the laser beam emitting unitis not particularly limited and may be suitably selected in accordancewith the intended use, however, the laser preferably has a wavelengthranging from the visible range to the infrared range, and morepreferably has a wavelength ranging from the near-infrared range to theinfrared range in terms of improvement in image contrast.

In the visible range, because additives used for absorbing the laserbeam and generating heat to record and erase an image on the thermallyreversible recording medium is colored, the image contrast may bereduced.

Since the wavelength of a laser beam emitted from the CO₂ laser is 10.6μm within the far-infrared region and the thermally reversible recordingmedium absorbs the laser beam, there is no need to add additives usedfor absorbing the laser beam and generating heat to record and erase animage on the thermally reversible recording medium. Further, theadditives sometimes absorb a visible light in a small amount even when alaser beam having a wavelength within the near-infrared range is used.Thus, the CO₂ laser that needs no addition of the additives has anadvantage in that it can prevent reduction in image contrast.

A wavelength of a laser beam emitted from the YAG laser, the fiber laseror the LD ranges from the visible range to the near-infrared range(several hundreds micrometers to 1.2 μm). Because an existing thermallyreversible recording medium does not absorb laser beam within thewavelength range, it is necessary to add a photothermal conversionmaterial for absorbing a laser beam and converting it into heat.However, these lasers respectively have an advantage in that a highlyfine image can be recorded because of the short wavelength thereof.

Further, because the YAG laser and the fiber laser are high-powerlasers, they have an advantage in that image recording and image erasingcan be speeded up. Since the LD is small in size, it is advantageous inthat it enables down-sizing of the equipment and low-production cost.

—Light Irradiation Intensity Controlling Unit—

The light irradiation intensity controlling unit has a function tochange a light irradiation intensity of the laser beam.

A location aspect of the light irradiation intensity controlling unit isnot particularly limited as long as the light irradiation intensitycontrolling unit is located on an optical path of a laser beam emittedfrom the laser beam emitting unit. A distance between the lightirradiation intensity controlling unit and the laser beam emitting unitmay be suitably adjusted in accordance with the intended use, however,it is preferable that the light irradiation intensity controlling unitbe located in between the laser beam emitting unit and a galvanomirrorwhich will be described hereinafter, and it is more preferable that thelight irradiation intensity controlling unit be located in between abeam expander which will be described hereinafter and the galvanomirror.

The light irradiation intensity controlling unit preferably has afunction to change a light intensity distribution of the laser beam,from a Gauss distribution, to a light intensity distribution in whichthe light intensity at a center portion is to be lower than the lightintensity in peripheral portions thereof and a light irradiationintensity I₁ at the center portion of the irradiated laser beam and alight irradiation intensity I₂ on an 80% light energy bordering surfaceto the total light energy of the irradiated laser beam satisfy theexpression, 0.40≦I₁/I₂≦2.00. With use of such a light irradiationintensity controlling unit, it is possible to prevent deterioration ofthe thermally reversible recording medium due to repeated recording anderasing and to improve the repetitive durability of the recording mediumwith maintaining an image contrast.

The light irradiation intensity controlling unit is not particularlylimited and may be suitably selected in accordance with the intendeduse, however, for example, lenses, filters, masks, mirrors andfiber-coupling devices are preferably exemplified. Of these, lenses arepreferable because they have less energy loss. For the lens, a collidescope, an integrator, a beam homogenizer, an aspheric beam shaper (acombination of an intensity conversion lens and a phase correctionlens), an aspheric device lens, a diffractive optical element or thelike can be preferably used. In particular, aspheric device lenses anddiffractive optical elements are preferable.

When a filter or a mask is used, the light irradiation intensity can becontrolled by physically cutting a center part of the laser beam. When amirror is used, the light irradiation intensity can be controlled byusing a deformable mirror which is capable of mechanically changing theshape of a light beam in conjunction with a computer or a mirror whosereflectance or surface convexoconcaves can be partially changed.

In the case of a laser having an oscillation wavelength of near-infraredlight or visible light, it is preferable to use it because the lightirradiation intensity can be easily controlled by fiber-coupling.Examples of the laser having an oscillation wavelength of near-infraredlight or visible light include laser diodes and solid lasers.

The method of controlling a light irradiation intensity using the lightirradiation intensity controlling unit will be described below in thedescription of the image processor of the present invention.

Hereinafter, one example of a method of controlling the lightirradiation intensity using an aspheric beam shaper as the lightirradiation intensity controlling unit will be described.

When a combination of an intensity conversion lens and a phasecorrection lens is used, as shown in FIG. 14A, two aspheric lenses arearranged on an optical path of a laser beam emitted from the laser beamemitting unit. Then, the light intensity is changed by a first asphericlens L1 from a target position (distance 1) so that a ratio I₁/I₂ issmaller than that in a Gauss distribution (in FIG. 14A, a lightintensity distribution is in a flat top-shaped pattern).

Thereafter, to make the light intensity-changed laser beam parallelytransmitted, the phase is corrected by means of a second aspheric lensL2. As a result, the light intensity distribution expressed as the Gaussdistribution can be converted.

As shown in FIG. 14B, only an intensity conversion lens L may be placedin an optical path of a laser beam emitted from the laser beam emittingunit. In this case, for the incident beam (laser beam) expressed as theGauss distribution, the light irradiation intensity at the centerportion in the light intensity distribution can be converted such thatthe ratio I₁/I₂ becomes small (in FIG. 14B a light intensitydistribution is in a flat top-shaped pattern) by diffusing the beam asrepresented by X1 in FIG. 14B at a high-intensity portion (innerportion), and by converging the beam at a weak-intensity portion (outerportion) as represented by X2.

Further, as the light irradiation intensity controlling unit, oneexample of a method of controlling a light irradiation intensity bymeans of a combination of a fiber-coupling laser diode and a lens willbe explained below.

In a fiber-coupling laser diode, since a laser beam is transmitted in afiber while repeating reflection, a light intensity distribution of alaser beam emitted from the fiber edge will be different from the Gaussdistribution and will be a light intensity distribution corresponding toan intermediate distribution pattern between the Gauss distribution andthe flat top-shaped distribution pattern. As a condensing opticalsystem, a combination unit of a plurality of convex lenses and/orconcave lenses is attached to the fiber edge so that such a lightintensity distribution is converted into the flat top-shapeddistribution pattern.

Here, one example of the image processor of the present invention isshown in FIG. 15, mainly explaining the laser beam emitting unit. In theimage processor of the present invention as shown in FIG. 15, forexample, a mask (not shown) for cutting a center part of a laser beam isincorporated as the light irradiation intensity controlling unit in anoptical path of a laser maker having a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.) to allow for controlling alight intensity distribution on a cross-section in the perpendiculardirection to the proceeding direction of the laser beam so that thelight irradiation intensity at the center portion in the light intensitydistribution changes to the light irradiation intensity of theperipheral portions.

The specification of an image-recording/erasing head part in the laserbeam emitting unit is as follows: available laser output range: 0.1 W to40 W; irradiation distance movable range: not particularly limited; spotdiameter: 0.18 mm to 10 mm; scanning speed range: 12,000 mm/s at themaximum; irradiation distance: 110 mm×110 mm; and focal distance: 185mm.

The image processor is equipped with at least the laser beam emittingunit and the light irradiation intensity controlling unit and may befurther equipped with an optical unit, a power source controlling unitand a program unit.

The optical unit is composed of a laser oscillator 110 as a laser beamemitting unit, a beam expander 102, a scanning unit 105, and an fθ lens106.

The beam expander 102 is an optical member in which a plurality oflenses are arranged, is located in between the laser oscillator 110 asthe laser beam emitting unit and galvanomirror to be describedhereinafter, and is configured to expand a laser beam emitted from thelaser oscillator 110 in a radius direction so as to establishsubstantially parallel laser beam.

The expansion rate of the laser beam is preferably ranging from 1.5times to 50 times, and the beam diameter at that time is preferably 3 mmto 50 mm.

The scanning unit 105 is composed of a galvanometer 104 andgalvanomirrors 104A mounted to the galvanometer 104. The twogalvanomirrors 104A attached in an X axis direction and a Y axisdirection on the galvanometer 104 are driven to rotationally scan alaser beam at high-velocity, thereby images can be recorded or erased ona thermally reversible recording medium 107. To enable image recordingand image erasing by photo-scanning at high-velocity, it is preferableto employ galvanomirror scanning method. The size of the galvanomirrorsdepends on the beam diameter of the parallel laser beam expanded by thebeam expander, and it is preferably in the range of 3 mm to 60 mm andmore preferably 6 mm to 40 mm.

When the beam diameter of the parallel beam is excessively reduced, thespot diameter of the laser beam condensed through the use of an fθ lensmay not be sufficiently reduced. In the meanwhile, when the beamdiameter of the parallel laser beam is excessively increased, thegalvanomirrors need to be increased in size, and the laser beam may notbe scanned at high velocity.

The fθ lens 106 is a lens to make a laser beam rotationally scanned atan equiangular velocity by the galvanomirrors 104A attached to thegalvanometer 104 move at a constant velocity on the surface of thethermally reversible recording medium 107.

The power source controlling unit is composed of an electricitydischarging power source (in the case of CO₂ laser) or a driving powersource for a light source that excites a laser medium (YAG laser etc.),a driving power source for a galvanometer, a cooling power source suchas peltiert device, a controlling unit configured to entirely controlthe operations of the image processor, and the like.

The program unit is a unit used to input conditions of laser beamintensity, laser beam scanning speed and the like for the purpose ofrecording or erasing images by inputting information with a touch panelor a keyboard and is also used to form and edit characters and the liketo be recorded.

The image processing method and the image processor respectively allowfor repeatedly recording and erasing a high-contrast image at high speedon a thermally reversible recording medium such as a label affixed to acontainer like corrugated fiberboard in a non-contact manner and allowsfor preventing deterioration of the thermally reversible recordingmedium due to repeated recording and erasing. Therefore, the imageprocessing method and the image processor of the present invention canbe particularly suitably used in logistical/physical distributionsystems. In this case, for example, an image can be recorded and erasedon the label while moving the corrugated fiberboard placed on a beltconveyer. Thus, the image processing method and the image processorenable shortening shipping time because there is no need to stopproduction lines. The corrugated fiberboard with the label attachedthereto can be reused just as it is without peeling off the labeltherefrom, and an image can be erased and recorded again on thecorrugated fiberboard.

Further, since the image processor has the light irradiation intensitycontrolling unit configured to change a light irradiation intensity of alaser beam, it can effectively prevent deterioration of the thermallyreversible recording medium due to repeated recording and erasing ofimages.

The present invention can solve the above-mentioned conventionalproblems and can provide an image processing method that allows forshortening a scanning direction of a scanning mirror and shorteningrecording time and erasing time than in recording and erasing an imageat a position nearer than a focal position of a laser beam used or atthe focal position and widening a recording area and an erasing area byplacing a thermally reversible recording medium at a position fartherthan the focal position of the laser beam and performing any one ofimage recording and image erasing, and can also provide an imageprocessor that can be preferably used in the image processing method.

The present invention can solve the above-mentioned conventionalproblems and can provide an image processing method that allows forpreventing an excessive amount of energy from being applied to eachoverlap portion where a plurality of image lines are overlapped witheach other and further to the entire image lines including start points,end points and straight lines constituting an image and preventingdeterioration of a thermally reversible recording medium by reducingdamage due to repeated image recording and image erasing, and can alsoprovide an image processor that can be preferably used in the imageprocessing method.

The present invention can solve the above-mentioned conventionalproblems and can provide an image processing method that allows foruniformly recording each image at a high-density and uniformly erasingthe recorded each image on the entire image lines including startpoints, end points and straight lines constituting an image andpreventing deterioration of a thermally reversible recording medium byreducing damage due to repeated image recording and image erasing, andcan also provide an image processor that can be preferably used in theimage processing method.

EXAMPLES

Hereinafter, the present invention will be further described in detailwith reference to Examples of the present invention, however, thepresent invention is not limited to the disclosed Examples.

Production Example 1 Preparation of Thermally Reversible RecordingMedium

A thermally reversible recording medium capable of reversibly changingin color tone between a transparent state and a color developed statedepending on temperature was prepared as follows.

—Substrate—

As a substrate, a white turbid polyester film of 125 μm in thickness(TETRON FILM U2L98W, manufactured by TEIJIN DUPONT FILMS JAPAN LTD.) wasused.

—Under Layer—

To 40 parts by mass of water, 30 parts by mass of a styrene-butadienecopolymer (PA-9159, manufactured by Nippon A & L Inc.), 12 parts by massof a polyvinyl alcohol resin (POVAL PVA103, manufactured by KURARAY Co.,Ltd.), and 20 parts by mass of a hollow particle (MICROSPHERE-300,manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.) were added to preparean under layer coating solution.

Next, the obtained under layer coating solution was applied over asurface of the substrate using a wire bar, and the applied coatingsolution was heated at 80° C. for 2 minutes and dried to thereby form anunder layer having a thickness of 20 μm.

—Reversible Thermosensitive Recording Layer (Recording Layer)—

Five parts by mass of a reversible developer represented by thefollowing Structural Formula (1), 0.5 parts by mass of a color-erasingaccelerator represented by the following Structural Formula (2), 0.5parts by mass of a color-erasing accelerator represented by thefollowing Structural Formula (3), 10 parts by mass of 50% by mass ofacrylpolyol solution (hydroxyl group value: 200 mgKOH/g) and 80 parts bymass of methylethylketone were pulverized and dispersed in a ball milluntil the average particle diameter became about 1 μm.

Next, in the dispersion liquid in which the reversible developer hadbeen pulverized and dispersed, 1 part by mass of2-anilino-3-methyl-6-dibutylaminofluoran as the leuco dye, 0.2 parts bymass of a phenol antioxidant represented by the following StructuralFormula (4) (IRGANOX 565, manufactured by Chiba Specialty ChemicalsK.K.) and 5 parts by mass of isocyanate (COLLONATE HL, manufactured byNippon Polyurethane Industry Co., Ltd.) were added, and the materialswere substantially stirred to prepare a recording layer coatingsolution.

Next, the obtained recording layer coating solution was applied over thesurface of the substrate with the under layer formed thereon using awire bar, and the applied coating solution was heated at 100° C. for 2minutes, dried and then cured at 60° C. for 24 hours to thereby form arecording layer having a thickness of 11 μm.

—Intermediate Layer—

Three parts by mass of 50% by mass acrylpolyol resin solution (LR327,manufactured by Mitsubishi Rayon Co., Ltd.), 7 parts by mass of 30% bymass zinc oxide fine particle dispersion liquid (ZS303, manufactured bySumitomo Cement Co., Ltd.), 1.5 parts by mass of isocyanate (COLLONATEHL, manufactured by Nippon Polyurethane Industry Co., Ltd.) and 7 partsby mass of methylethylketone were substantially stirred to prepare anintermediate layer coating solution.

Next, over the surface of the substrate with the under layer and therecording layer formed thereon, the intermediate coating solution wasapplied using a wire bar, and the applied coating solution was heated at90° C. for 1 minute, dried, and then heated at 60° C. for 2 hours tothereby form an intermediate layer having a thickness of 2 μm.

—Protective Layer—

Three parts by mass of pentaerythritol hexaacrylate (KAYARAD DPHA,manufactured by Nippon Kayaku Co., Ltd.), 3 parts by mass of urethaneacrylate oligomer (ART RESIN UN-3320HA, manufactured by Negami ChemicalIndustrial Co., Ltd.), 3 parts by mass of acrylic ester ofdipentaerithritol caprolactone (KAYARAD DPCA-120, manufactured by NipponKayaku Co., Ltd.), 1 part by mass of silica (P-526, manufactured byMizusawa Chemical Industries Co., Ltd.), 0.5 parts by mass of aphotopolymerization initiator (IRGACURE 184, manufactured by Chiba GeigyJapan Co., Ltd.) and 11 parts by mass of isopropyl alcohol were stirredin a ball mill and dispersed until the average particle diameter becameabout 3 μm to prepare a protective layer coating solution.

Next, over the surface of the substrate with the under layer, therecording layer and the intermediate layer formed thereon, theprotective layer coating solution was applied using a wire bar, and theapplied coating solution was heated at 90° C. for 1 minute, dried andthen crosslinked by means of an ultraviolet lamp of 80 W/cm to therebyform a protective layer having a thickness of 4 μm.

—Back Layer—

In a ball mill, 7.5 parts by mass of pentaerythritol hexaacrylate(KARAYAD DPHA, manufactured by Nippon Kayaku Co., Ltd.), 2.5 parts bymass of urethane acrylate oligomer (ART RESIN UN-3320HA, manufactured byNegami Chemical Industrial Co., Ltd.), 2.5 parts by mass of aneedle-like conductive titanium oxide (FT-3000, manufactured by ISHIHARAINDUSTRY CO., LTD., major axis=5.15 μm, minor axis=0.27 μm, composition:titanium oxide coated with antimony-doped tin oxide), 0.5 parts by massof a photopolymerization initiator (IRGACURE 184, manufactured by ChibaGeigy Japan Co., Ltd.) and 13 parts by mass of isopropyl alcohol weresubstantially stirred to prepare a back layer coating solution.

Next, over the opposite surface of the substrate from the surface onwhich the recoating layer, the intermediate layer and the protectivelayer had been formed, the back layer coating solution was applied usinga wire bar, and the applied coating solution was heated at 90° C. for 1minute, dried and then crosslinked by means of an ultraviolet lamp of 80W/cm to thereby form a back layer having a thickness of 4 μm. With theabove-mentioned treatments, a thermally reversible recording layer ofProduction Example 1 was prepared.

Production Example 2 Preparation of thermally reversible recordingmedium

A thermally reversible recording medium capable of reversibly changingin color tone between a transparent state and a color developed statedepending on temperature was prepared as follows.

—Substrate—

As a substrate, a transparent PET film of 175 μm in thickness (LUMILAR175-T12, manufactured by Toray Industries, Inc.) was used.

—Reversible Thermosensitive Recording Layer (Recording Layer)—

In a resin solution in which 26 parts by mass of vinyl chloridecopolymer (M110, manufactured by ZEON CORPORATION) had been dissolved in210 parts by mass of methylethylketone, and 3 parts by mass of anorganic low-molecular material represented by the following StructuralFormula (5) and 7 parts by mass of dococyl behenate were added. Aceramic bead having a diameter of 2 mm was put in a glass bottle, andthe prepared solution was poured thereto. The solution was dispersedusing a paint shaker (manufactured by Asada Tekko Co., Ltd.) for 48hours to prepare a uniform dispersion liquid.

Next, to the obtained dispersion liquid, 4 parts by mass of anisocyanate compound (COLLONATE 2298-90T, manufactured by NipponPolyurethane Industry Co., Ltd.) was added to prepare a thermosensitiverecording layer coating solution.

Next, over the surface of the substrate (PET film adhesive layer havinga magnetic recording layer), the obtained thermosensitive recordinglayer coating solution was applied, and the applied coating solution washeated, dried and then stored under a temperature of 65° C. for 24 hoursso as to be crosslinked, thereby forming a thermosensitive recordinglayer having a thickness of 10 μm.

—Protective Layer—

A solution composed of 10 parts by mass of 75% by mass butyl acetatesolution of urethane acrylate ultraviolet curable resin (UNIDICK C7-157,manufactured by Dainippon Ink and Chemicals, Inc.) and 10 parts by massof isopropyl alcohol was applied over the thermosensitive recordinglayer using a wire bar, heated, dried and then irradiated withultraviolet ray using a high-pressure mercury lamp of 80 W/cm to becured, thereby forming a protective layer having a thickness of 3 μm.With the above-mentioned treatments, a thermally reversible recordingmedium of Production Example 2 was prepared.

Production Example 3 Preparation of Thermally Reversible RecordingMedium

A thermally reversible recording medium of Production Example 3 wasprepared in the same manner as in Production Example 1 except that 0.03parts by mass of a photothermal conversion material (EXCOLOR IR-14,manufactured by NIPPON SHOKUBAI CO., LTD.) was added in the preparationof the thermally reversible recording medium.

Production Example 4 Preparation of Thermally Reversible RecordingMedium

A thermally reversible recording medium of Production Example 4 wasprepared in the same manner as in Production Example 2 except that 0.07parts by mass of the photothermal conversion material (EXCOLOR IR-14,manufactured by NIPPON SHOKUBAI CO., LTD.) was added in the preparationof the thermally reversible recording medium.

(Evaluation Method) <Measurement of Laser Beam Intensity Distribution>

A laser beam intensity distribution was measured according to thefollowing procedures.

When a laser diode device was used as a laser, first a laser beamanalyzer (SCORPION SCOR-20SCM, manufactured by Point Grey Research Co.)was set such that the irradiation distance was adjusted at the sameposition as in recording on the thermally reversible recording medium,the laser beam was attenuated using a beam splitter composed of atransmission mirror in combination with a filter (BEAMSTAR-FX-BEAMSPLITTER, manufactured by OPHIR Co.) so that the output power of thelaser beam was 3×10⁻⁶, and a light intensity of the laser beam wasmeasured using the laser beam analyzer. Next, the obtained laser beamintensity was three-dimensionally graphed to thereby obtain a lightintensity distribution of the laser beam.

When a CO₂ laser device was used as a laser, a laser beam emitted fromthe CO₂ laser device was attenuated using a Zn—Se wedge (LBS-100-1R-W,manufactured by Spiricon Inc.) and a CaF₂ filter (LBS-100-1R-F,manufactured by Spiricon Inc.), and a light intensity of the laser beamwas measured using a high-powered laser beam analyzer (LPK-CO₂-16,manufactured by Spiricon Inc.).

<Measurement of Reflectance Density>

A reflectance density was measured as follows. A gray scale image wasretrieved on a Gray Scale (manufactured by Kodak AG.) with a scanner(CANOSCAN4400, manufactured by Canon Inc.), the obtained digital grayscale values were correlated with density values measured by means of areflectance densitometer (RD-914, manufactured by Macbeth Co.).Specifically, a gray scale image of an erased portion where an image hadbeen recorded and then erased was retrieved with the scanner, and then adigital gray scale value of the obtained gray scale image was convertedinto a density value, and the density value was regarded as areflectance density value.

In the present invention, when a thermally reversible recording mediumhaving a thermally reversible recording layer which contained a resinand an organic low-molecular material was evaluated, and the density ofan erased portion was 0.15 or more, it was recognized that it waspossible to erase the recorded image, and when a thermally reversiblerecording medium having a thermally reversible recording layer whichcontained a leuco dye and a reversible developer was evaluated, and thedensity of an erased portion was 0.15 or less, it was recognized that itwas possible to erase the recorded image. Note that in the case of athermally reversible recording medium having a thermally reversiblerecording layer which contained a resin and an organic low-molecularmaterial, a reflectance density was measured after setting a black papersheet (O.D. value=1.7) under the thermally reversible recording medium.

Example A-1 Image Recording Step

A laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.) was used, the thermallyreversible recording medium of Production Example 1 was placed at aposition 5 mm away from a focal position, and the laser marker wascontrolled such that the output power of the laser beam was 11.0 W, theirradiation distance was 190 mm, the spot diameter was 0.56 mm and thescanning speed was 2,000 mm/s. Then, characters of “A” to “Z” of 5 mm×5mm in size were recorded twice on the thermally reversible recordingmedium of Production Example 1 using the laser marker. The recordingtime was 0.73 seconds. A ratio I₁/I₂ in the light intensity distributionof the laser beam at this point in time was 2.30.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.027.

Further, the spot diameter at the focal position was 0.18 mm, and whenthe spot diameter of a laser beam at the focal position was representedby “A” and the spot diameter of the laser beam on the thermallyreversible recording medium was represented by “B”, a value B/A was 3.1

—Image Erasing Step—

Subsequently, the thermally reversible recording medium was heated at140° C. for 1 second under a pressure of 1 kgf/cm² using a heatinclination tester (TYPE HG-100, manufactured by TOYO SEIKI Co., Ltd.).

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of an erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-2 Image Recording Step

A laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.) was used, the thermallyreversible recording medium of Production Example 1 was placed at aposition 9 mm away from a focal position, and the laser marker wascontrolled such that the output power of the laser beam was 15.0 W, theirradiation distance was 194 mm, the spot diameter was 0.87 mm and thescanning speed was 2,000 mm/s. Then, characters of “A” to “Z” of 5 mm×5mm in size were recorded twice on the thermally reversible recordingmedium of Production Example 1 using the laser marker. The recordingtime was 0.71 seconds. A ratio I₁/I₂ in the light intensity distributionof the laser beam at this point in time was 2.30.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.05.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 4.83.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-3 Image Recording Step

A laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.) was used, the thermallyreversible recording medium of Production Example 1 was placed at aposition 46 mm away from a focal position, and the laser marker wascontrolled such that the output power of the laser beam was 39.0 W, theirradiation distance was 210 mm, the spot diameter was 2.0 mm and thescanning speed was 2,000 mm/s. Then, characters of “A” to “Z” of 5 mm×5mm in size were recorded twice on the thermally reversible recordingmedium of Production Example 1 using the laser marker. The recordingtime was 0.65 seconds. A ratio I₁/I₂ in the light intensity distributionof the laser beam at this point in time was 2.30.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.14.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 11.1.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium. Further,the thermally reversible recording medium was affixed to another plasticbox, the plastic box was placed on the conveyer, and characters of “A”to “Z” of mm×5 mm in size were recorded twice on the thermallyreversible recording medium under the recording conditions in the imagerecording step while moving the conveyer at a conveying speed of 10m/min. The travel time of the thermally reversible recording medium was0.66 seconds. As a result, it was possible to record all the charactersof “A” to “Z” twice on the thermally reversible recording medium.

Example A-4 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask having a hole of 6 mmin diameter at a center part thereof was incorporated in the opticalpath of the laser beam.

Next, the laser marker was controlled such that the output power of thelaser beam was 20.0 W. the irradiation distance was 205. 0 mm, the spotdiameter was 0.70 mm and the scanning speed was 2,000 mm/s. Then,characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice on thethermally reversible recording medium of Production Example 1 using thelaser marker. The recording time was 0.68 seconds. A ratio I₁/I₂ in thelight intensity distribution of the laser beam at this point in time was1.97.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.11.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 3.89.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-5 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam.

Next, the laser marker was controlled such that the output power of thelaser beam was 28.0 W, the irradiation distance was 198. 0 mm, the spotdiameter was 0.65 mm and the scanning speed was 2,000 mm/s. Then,characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice on thethermally reversible recording medium of Production Example 1 using thelaser marker. The recording time was 0.70 seconds. A ratio I₁/I₂ in thelight intensity distribution of the laser beam at this point in time was1.60.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.07.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was 10 representedby “A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 3.61.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-6 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam.

Next, the laser marker was controlled such that the output power of thelaser beam was 36.0 W, the irradiation distance was 200.5 mm, the spotdiameter was 0.95 mm and the scanning speed was 2,000 mm/s. Then,characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice on thethermally reversible recording medium of Production Example 1 using thelaser marker. The recording time was 0.70 seconds. A ratio I₁/I₂ in thelight intensity distribution of the laser beam at this point in time was0.56.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.08.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 5.28.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-7 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam.

Next, the laser marker was controlled such that the output power of thelaser beam was 36.0 W, the irradiation distance was 202.0 mm, the spotdiameter was 1.0 mm and the scanning speed was 2,000 mm/s. Then,characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice on thethermally reversible recording medium of Production Example 1 using thelaser marker. The recording time was 0.69 seconds. A ratio I₁/I₂ in thelight intensity distribution of the laser beam at this point in time was0.40.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.09.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 5.56.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-8 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask having a hole of 6 mmin diameter at a center part thereof was incorporated in the opticalpath of the laser beam.

Next, the laser marker was controlled such that the output power of thelaser beam was 20.0 W. the irradiation distance was 203.5 mm, the spotdiameter was 0.65 mm and the scanning speed was 2,000 mm/s. Then,characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice on thethermally reversible recording medium of Production Example 1 using thelaser marker. The recording time was 0.69 seconds. A ratio I₁/I₂ in thelight intensity distribution of the laser beam at this point in time was2.08.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.10.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 3.61.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-9 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam.

Next, the laser marker was controlled such that the output power of thelaser beam was 38.0 W, the irradiation distance was 205.0 mm, the spotdiameter was 1.1 mm and the scanning speed was 2,000 mm/s. Then,characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice on thethermally reversible recording medium of Production Example 1 using thelaser marker. The recording time was 0.68 seconds. A ratio I₁/I₂ in thelight intensity distribution of the laser beam at this point in time was0.35.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.11.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 6.11.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium.

Example A-10 Image Recording Step

The image was recorded in the same manner as in Example A-5.

Subsequently, the laser marker of Example A-1 was used and controlledsuch that the output power of the laser beam was 32.0 W, the irradiationdistance was 200 mm, the spot diameter was 1.3 mm and the scanning speedwas 11,000 mm/s. The laser beam was applied to an area of 10 mm×50 mm ofthe thermally reversible recording medium to erase the image recorded onthe thermally reversible recording medium. The erasing time was 0.63seconds.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.08.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 7.2.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium with the image recordedthereon in the image recording step was affixed to a plastic box, theplastic box was placed on a conveyer, and the image was erased under theerasing conditions in the image erasing step while moving the conveyerat a conveying speed of 9 m/min. The travel time of the thermallyreversible recording medium was 0.74 seconds. As a result, it waspossible to completely erase the image in the area of 10 mm×50 mm.

Example A-11

The image was recorded in the same manner as in Example A-5.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-10 except that the laser marker used in Example A-1 was used,and the laser marker was controlled such that the output power of thelaser beam was 32 W, the irradiation distance was 277.5 mm, the spotdiameter was 6.9 mm, and the scanning speed was 1,000 mm/s. The erasingtime was 0.71 seconds.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.5.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 38.0.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium with the image recordedthereon in the image recording step was affixed to a plastic box, theplastic box was placed on a conveyer, and the image was erased under theerasing conditions in the image erasing step while moving the conveyerat a conveying speed of 9 m/min. The travel time of the thermallyreversible recording medium was 0.74 seconds. As a result, it waspossible to completely erase the image in the area of 10 mm×50 mm.

Example A-12

The image was recorded in the same manner as in Example A-5.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-10 except that the laser marker used in Example A-1 was used,and the laser marker was controlled such that the output power of thelaser beam was 32 W, the irradiation distance was 388 mm, the spotdiameter was 15.0 mm, and the scanning speed was 250 mm/s. The erasingtime was 1.5 seconds.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 2.1.

Further, the spot diameter at the focal position was 0.18 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 83.3.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium with the image recordedthereon in the image recording step was affixed to a plastic box, theplastic box was placed on a conveyer, and the image was erased under theerasing conditions in the image erasing step while moving the conveyerat a conveying speed of 9 m/min. As a result, it was impossible tocompletely erase the image in the area of 10 mm×50 mm.

Example A-13

Image recording and image erasing were performed in the same manner asin Example A-11 except that the thermally reversible recording mediumwas used instead of the thermally reversible recording medium ofProduction Example 1, and the output power of the laser beam at the timeof recording the image was set to 16.8 W, and the output power of thelaser beam at the time of erasing the image was set to 22.4 W. The imagerecording time was 0.70 seconds, and the image erasing time was 0.71seconds.

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium. Further,the thermally reversible recording medium with the image recordedthereon in the image recording step was affixed to another plastic box,the plastic box was placed on the conveyer, and the image was erasedunder the erasing conditions in the image erasing step while moving theconveyer at a conveying speed of 9 m/min. As a result, it was possibleto completely erase the image in the area of 10 mm×50 mm.

Example A-14 Image Recording Step

As a laser, a fiber-coupling high-powered laser diode device of laseroutput power 25 W (LIMO25-F100-DL808, manufactured by LIMO Co., centerwavelength: 808 nm, optical fiber core diameter: 100 μm, and lens NA:0.11) equipped with a condenser optical system of fθ lens (focaldistance: 150 mm) was used. A mask for cutting a center part of a laserbeam was incorporated in the optical path of the laser beam.

Next, the laser diode device was controlled such that the output powerof the laser beam was 22 W, the irradiation distance was 158 mm, and thespot diameter was about 1.2 mm. Then, characters of “A” to “Z” of 5 mm×5mm in size were recorded twice on the thermally reversible recordingmedium of Production Example 3 at a photo-scanning speed of 2,000 usinggalvanomirrors. The recording time was 0.71 seconds.

A ratio I₁/I₂ in the light intensity distribution of the laser beam atthis point in time was 1.85.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.05.

Further, the spot diameter at the focal position was 0.74 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 1.62.

—Image Erasing Step—

Subsequently, the mask for cutting a center part of a laser beam wasremoved from the optical path of the laser beam, and the laser diodedevice was controlled such that the output power of the laser beam was20 W, the irradiation distance was 195 mm, the spot diameter was 3 mm,and the scanning speed was 1,000 mm/s. Then, the image recorded on thethermally reversible recording medium was erased with irradiating thelaser beam in an area of 5 mm×50 mm on the thermally reversiblerecording medium. The erasing time was 0.70 seconds.

A ratio I₁/I₂ in the light intensity distribution of the laser beam atthis point in time was 1.70.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.3.

Further, the spot diameter at the focal position was 0.74 mm, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 4.05.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium. Further,the thermally reversible recording medium with the image recordedthereon in the image recording step was affixed to a plastic box, theplastic box was placed on the conveyer, and the image was erased underthe erasing conditions in the image erasing step while moving theconveyer at a conveying speed of 9 m/min. As a result, it was possibleto completely erase the image in the area of 5 mm×50 mm.

Example A-15

Image recording and image erasing were performed in the same manner asin Example A-14 except that the thermally reversible recording medium ofProduction Example 4 was used instead of the thermally reversiblerecording medium of Production Example 3, the output power of the laserbeam at the time of recording the image was set to 15.5 W and the outputpower of the laser beam at the time of erasing the image was set to 14.0W. The image recording time was 0.71 seconds, and the image erasing timewas 0.70 seconds.

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, the thermally reversible recording medium was affixed to a plasticbox, the plastic box was placed on a conveyer, and characters of “A” to“Z” of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium under the recording conditions in the image recordingstep while moving the conveyer at a conveying speed of 9 m/min. Thetravel time of the thermally reversible recording medium was 0.74seconds. As a result, it was possible to record all the characters of“A” to “Z” twice on the thermally reversible recording medium. Further,the thermally reversible recording medium with the image recordedthereon in the image recording step was affixed to a plastic box, theplastic box was placed on the conveyer, and the image was erased underthe erasing conditions in the image erasing step while moving theconveyer at a conveying speed of 9 m/min. As a result, it was possibleto completely erase the image in the area of 5 mm×50 mm.

Comparative Example A-1 Image Recording Step

The laser marker used in Example A-1 was used, the thermally reversiblerecording medium of Production Example 1 was placed, and the lasermarker was controlled such that the output power of the laser beam was7.1 W. the irradiation distance was 185 mm, the spot diameter was 0.18mm and the scanning speed was 2,000 mm/s. Then, characters of “A” to “Z”of 5 mm×5 mm in size were recorded twice on the thermally reversiblerecording medium of Production Example 1. The recording time was 0.75seconds. A ratio I₁/I₂ in the light intensity distribution of the laserbeam at this point in time was 2.30.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 1.0. Further, when a spot diameter of a laser beam at the focalposition was represented by “A” and a spot diameter of the laser beam onthe thermally reversible recording medium was represented by “B”, avalue B/A was 1.0.

—Image Erasing Step—

Subsequently, the recorded image was erased in the same manner as inExample A-1.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, a thermally reversible recording medium on which the image hadbeen recorded thereon in the same manner as in the image recording stepwas affixed to a plastic box, the plastic box was placed on a conveyer,and characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice onthe thermally reversible recording medium under the recording conditionsin the image recording step while moving the conveyer at a conveyingspeed of 9 m/min. The travel time of the thermally reversible recordingmedium was 0.74 seconds. As a result, it was impossible to record allthe characters of “A” to “Z” twice on the thermally reversible recordingmedium.

Comparative Example A-2 Image Recording Step

A laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.) was used, the thermallyreversible recording medium of Production Example 1 was placed at aposition 11 mm nearer than a focal position, and the laser marker wascontrolled such that the output power of the laser beam was 26.0 W. theirradiation distance was 174 mm, the spot diameter was 1.0 mm and thescanning speed was 2,000 mm/s. Then, characters of “A” to “Z” of 5 mm×5mm in size were recorded twice on the thermally reversible recordingmedium of Production Example 1. The recording time was 0.79 seconds. Aratio I₁/I₂ in the light intensity distribution of the laser beam atthis point in time was 2.30.

Note that for the setting position of the thermally reversible recordingmedium, when a distance from a laser light source to a focal positionwas represented by “X” and a distance from the laser light source to thethermally reversible recording medium was represented by “Y”, a value ofY/X was 0.94.

Further, the spot diameter at the focal position was 0.18, and when aspot diameter of a laser beam at the focal position was represented by“A” and a spot diameter of the laser beam on the thermally reversiblerecording medium was represented by “B”, a value B/A was 5.6.

—Image Erasing Step—

The recorded image was erased in the same manner as in Example A-10except that the laser marker was controlled so that the output power ofthe laser beam was 22.0 W, the irradiation distance was 155 mm, the spotdiameter was 2.0 mm, and the scanning speed was 3,000 mm/s. The imageerasing time was 0.90 seconds.

—Evaluation of Repetitive Durability—

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of the erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 1 shows the results.

Next, a thermally reversible recording medium on which the image hadbeen recorded thereon in the same manner as in the image recording stepwas affixed to a plastic box, the plastic box was placed on a conveyer,and characters of “A” to “Z” of 5 mm×5 mm in size were recorded twice onthe thermally reversible recording medium under the recording conditionsin the image recording step while moving the conveyer at a conveyingspeed of 9 m/min. The travel time of the thermally reversible recordingmedium was 0.74 seconds. As a result, it was impossible to record allthe characters of “A” to “Z” twice on the thermally reversible recordingmedium.

Further, the thermally reversible recording medium with the imagerecorded thereon in the image recording step was affixed to anotherplastic box, the plastic box was placed on the conveyer, and the imagewas erased under the erasing conditions in the image erasing step whilemoving the conveyer at a conveying speed of 9 m/min. The travel time ofthe thermally reversible recording medium was 0.74 seconds. As a result,it was impossible to completely erase the image in the area of 10 mm×50mm.

TABLE 1 I₁/I₂ at the Number of repeatedly rewritable time times Y/X B/Aof recording Ex. A-1 50 1.027 3.1 2.3 Ex. A-2 50 1.05 4.83 2.3 Ex. A-360 1.14 11.1 2.3 Ex. A-4 290 1.11 3.89 1.97 Ex. A-5 470 1.07 3.61 1.6Ex. A-6 420 1.08 5.28 0.56 Ex. A-7 350 1.09 5.56 0.4 Ex. A-8 100 1.103.61 2.08 Ex. A-9 210 1.11 6.11 0.35 Ex. A-10 460 1.08 7.2 1.6 Ex. A-11460 1.50 38.0 1.6 Ex. A-12 460 2.10 83.3 1.6 Ex. A-13 650 1.50 38.0 1.6Ex. A-14 410 1.05 1.62 1.85 Ex. A-15 590 1.05 1.62 1.85 Compara. 50 1.01.0 2.3 Ex. A-1 Compara. 50 0.94 5.6 2.3 Ex. A-2

Example B-1

Using the thermally reversible recording medium of Production Example 3,image processing was performed as follows, and repetitive durability ofthe thermally reversible recording medium was evaluated. Table 2 showsthe evaluation results.

—Image Recording Step—

As a laser, a fiber-coupling high-powered laser diode device of laseroutput power 140 W (NBT-S140mk II, manufactured by Jena Optics GmbH;center wavelength: 808 nm, optical fiber core diameter: 600 μm, and NA:0.22) equipped with a condenser optical system f100 was used as a laser,and the laser diode device was controlled so that the output power ofthe laser beam was 12 W, the irradiation distance was 91 mm and the spotdiameter was about 0.55 mm. Using the laser diode device, a character“V” was recorded on the thermally reversible recording medium ofProduction Example 3 at a feed rate of 1,200 mm/s of the XY stage inaccordance with the recording method as shown in FIG. 4A. Specifically,as shown in FIG. 4A, the thermally reversible recording medium wasirradiated with the laser beam, and an image 1 was recorded in a D1direction. Here, irradiation of the laser beam was stopped, the focalpoint of the laser beam irradiation was moved to a start point of animage line 2, and then the image line 2 was recorded in a D2 direction.At an overlap portion T, the end point of the image line 1 wasoverlapped with the end point of the image line 2, and the image line 1and image line 2 were recorded in a non-continuous manner.

At that time, a light intensity distribution of the laser beam wasmeasured, a light intensity distribution curve as shown in FIG. 3C wasobtained, and the ratio I₁/I₂ was 1.75.

—Image Erasing Step—

Subsequently, the laser diode device was controlled so that the outputpower of the laser beam was 15 W, the irradiation distance was 86 mm,and the spot diameter was 4.0 mm, and the image of the character “V”recorded on the thermally reversible recording medium was erased usingthe laser diode device at a feed rate of the XY stage, 1,200 mm/s.

<Evaluation of Repetitive Durability>

The image recording step and the image erasing step were repeatedlyperformed and finally, the erasing step was performed. Reflectancedensities of an erased portion at the overlap portion of the character“X” and portions other then the overlap portion on the thermallyreversible recording medium were measured to evaluate the image. Eachreflectance density was measured as follows. A gray scale image wasretrieved on a Gray Scale (manufactured by Kodak AG.) with a scanner(CANOSCAN4400, manufactured by Canon Inc.), the obtained digital grayscale values were correlated with density values measured by means of areflectance densitometer (RD-914, manufactured by Macbeth Co.).Specifically, a gray scale image of an erased portion where an image hadbeen recorded and then erased was retrieved with the scanner, and then adigital gray scale value of the obtained gray scale image was convertedinto a density value, and the density value was regarded as areflectance density value.

In the present invention, when a thermally reversible recording mediumhaving a thermally reversible recording layer which contained a resinand an organic low-molecular material was evaluated, and the density ofan erased portion was 0.15 or more, it was recognized that it waspossible to erase the recorded image, and when a thermally reversiblerecording medium having a thermally reversible recording layer whichcontained a leuco dye and a reversible developer was evaluated, and thedensity of an erased portion was 0.15 or less, it was recognized that itwas possible to erase the recorded image. Note that in the case of athermally reversible recording medium having a thermally reversiblerecording layer which contained a resin and an organic low-molecularmaterial, a reflectance density was measured after setting a black papersheet (O.D. value=1.7) under the thermally reversible recording medium.

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of an erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 2 shows the results.

<Measurement of Laser Beam Intensity Distribution>

A laser beam intensity distribution was measured according to thefollowing procedures.

When a laser diode device was used as a laser, first a laser beamanalyzer (SCORPION SCOR-20SCM, manufactured by Point Grey Research Co.)was set such that the irradiation distance was adjusted at the sameposition as in recording on the thermally reversible recording medium,the laser beam was attenuated using a beam splitter composed of atransmission mirror in combination with a filter (BEAMSTAR-FX-BEAMSPLITTER, manufactured by OPHIR Co.) so that the output power of thelaser beam was 3×10⁻⁶, and a light intensity of the laser beam wasmeasured using the laser beam analyzer. Next, the obtained laser beamintensity was three-dimensionally graphed to thereby obtain a lightintensity distribution of the laser beam.

When a CO₂ laser device was used as a laser, a laser beam emitted fromthe CO₂ laser device was attenuated using a Zn—Se wedge (LBS-100-1R-W,manufactured by Spiricon Inc.) and a CaF₂ filter (LBS-100-1R-F,manufactured by Spiricon Inc.), and a light intensity of the laser beamwas measured using a high-powered laser beam analyzer (LPK-CO₂-16,manufactured by Spiricon Inc.).

Example B-2

As a laser, a fiber-coupling high-powered laser diode device of laseroutput power 25 W (LIMO25-F100-DL808, manufactured by LIMO Co., centerwavelength: 808 nm, optical fiber core diameter: 100 μm, and lens NA:0.11) equipped with a condenser optical system of fθ lens (focaldistance: 150 mm) was used. The laser diode device was controlled suchthat the output power of the laser beam was 10 W, the irradiationdistance was 150 mm, and the spot diameter was about 0.75 mm. Then, acharacter of “V” was recorded on the thermally reversible recordingmedium of Production Example 3 at a photo-scanning speed of 1,200 mm/susing galvanomirrors according to the recording method illustrated inFIG. 4A.

A ratio I₁/I₂ in the light intensity distribution of the laser beam atthis point in time was 1.65.

In the image erasing step, the laser diode device was controlled suchthat the output power of the laser beam was 20 W, the irradiationdistance was 195 mm, the spot diameter was 3 mm, and the scanning speedwas 1,000 mm/s. Then, the recorded image was erased while linearlyscanning the laser beam at 0.59 mm intervals. A ratio I₁/I₂ in the lightintensity distribution of the laser beam at this point in time was 1.70.

Other conditions were set under the same conditions as in Example B-1and repetitive durability of the thermally reversible recording mediumwas evaluated. Table 2 shows the evaluation results.

Example B-3

Image recording and image erasing were performed in the same manner asin Example B-1 except that the thermally reversible recording medium ofProduction Example 4 was used instead of the thermally reversiblerecording medium of Production Example 3. Repetitive durability of thethermally reversible recording medium was evaluated in the same manneras in Example 1. Table 2 shows the evaluation results.

Example B-4

Image recording and image erasing were performed in the same manner asin Example B-2 except that in the image recording step, a character “V”was recorded according to the recording method illustrated in FIG. 4B.Repetitive durability of the thermally reversible recording medium wasevaluated in the same manner as in Example B-2. Table 2 shows theevaluation results.

In the recording method illustrated in FIG. 4B, the thermally reversiblerecording medium was irradiated with the laser beam, and an image line 1was recorded in a D3 direction. Here, irradiation of the laser beam wasstopped, the focal point of the laser beam irradiation was moved to astart point of an image line 2 (an overlap portion T), and the imageline 2 was recorded in a D4 direction. At the overlap portion T, thestart point of the image line 1 was overlapped with the start point ofthe image line 2, and the image line 1 and the image line 2 wererecorded in a non-continuous manner.

Example B-5

Image recording and image erasing were performed in the same manner asin Example B-2 except that in the image recording step, the recordingmethod of a character “V” as illustrated in FIG. 4C was changed so thatan image line 1 and an image line 2 were recorded in a non-continuousmanner, as described below. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample B-1. Table 2 shows the evaluation results.

In Example B-5, in the recording method of a character “V” asillustrated in FIG. 4C, the thermally reversible recording medium wasirradiated with a laser beam, and an image line 1 was recorded in a D1direction. Here, irradiation of the laser beam was stopped, and from anoverlap portion T again, an image line 2 was recorded in a D4 direction.In this case, at the overlap portion T, the end point of the image line1 was overlapped with the start point of the image line 2, however,these image lines were recorded in a non-continuous manner.

Example B-6

Image recording step and image erasing step were performed in the samemanner as in Example B-2 except that in the image recording step, thefocal distance was changed to 160 mm, and the output power of the laserbeam was changed to 11 W. A ratio I₁/I₂ in the light intensitydistribution of the laser beam was 2.00. Repetitive durability of thethermally reversible recording medium was evaluated in the same manneras in Example B-2. Table 2 shows the evaluation results.

Example B-7

Image recording and image erasing were performed in the same manner asin Example B-2 except that in the image recording step, the focaldistance was changed to 144 mm, and the output power of the laser beamwas changed to 13 W. A ratio I₁/I₂ in the light intensity distributionof the laser beam was 0.40. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample B-2. Table 2 shows the evaluation results.

Example B-8

Image recording and image erasing were performed in the same manner asin Example B-2 except that in the image recording step, the focaldistance was changed to 163 mm, and the output power of the laser beamwas changed to 11 W. A ratio I₁/I₂ in the light intensity distributionof the laser beam was 2.05. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample B-2. Table 2 shows the evaluation results.

Example B-9

Image recording and image erasing were performed in the same manner asin Example B-2 except that in the image recording step, the focaldistance was changed to 143 mm, and the output power of the laser beamwas changed to 14 W. A ratio I₁/I₂ in the light intensity distributionof the laser beam was 0.34. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample B-2. Table 2 shows the evaluation results.

Example B-10 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam. The laser marker was controlled so that a ratio I₁/I₂ in the lightintensity distribution of the laser beam was 1.60.

Next, the laser marker was controlled so that the output power of thelaser beam of 14.0 W, the irradiation distance was 198 mm, the spotdiameter was 0.65 mm, and the scanning speed was 1,000 mm/s. Then, usingthe laser marker, a character of “V” was recorded on the thermallyreversible recording medium of Production Example 1 according to therecording method as illustrated in FIG. 4A.

<Image Erasing Step>

Subsequently, the mask for cutting a center part of a laser beam wasremoved from the optical path of the laser beam, and the laser diodedevice was controlled such that the output power of the laser beam was22 W, the irradiation distance was 155 mm, the spot diameter was about 2mm, and the scanning speed was 3,000 mm/s. Then, the image of thecharacter “V” recorded on the thermally reversible recording medium waserased.

Example B-11 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam. The laser marker was controlled so that a ratio I₁/I₂ in the lightintensity distribution was 1.60.

Next, the laser marker was controlled so that the output power of thelaser beam was 12.0 W, the irradiation distance was 198 mm, the spotdiameter was 0.65 mm, and the scanning speed was 1,000 mm/s. Then, usingthe laser marker, a character of “V” was recorded on the thermallyreversible recording medium of Production Example 2 according to therecording method as illustrated in FIG. 4A.

<Image Erasing Step>

Subsequently, the mask for cutting a center part of a laser beam wasremoved from the optical path of the laser beam, and the laser markerwas controlled such that the output power of the laser beam was 17 W,the irradiation distance was 155 mm, the spot diameter was about 2 mm,and the scanning speed was 3,000 mm/s. Then, the image of character “V”recorded on the thermally reversible recording medium was erased.

Next, repetitive durability of the thermally reversible recording mediumwas evaluated in the same manner as in Example B-1. Table 2 shows theevaluation results.

Comparative Example B-1

Image recording and image erasing were performed in the same manner asin Example B-2 except that in the recording step, a character of “V” wasrecorded in a continuous manner according to the recording method asillustrated in FIG. 4C. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample B-2. Table 2 shows the evaluation results.

In the recording method as illustrated in FIG. 4C, the thermallyreversible recording medium was irradiated with the laser beam, and animage line 1 was recorded in a D1 direction. Then, an image line 2 wasrecorded in a D4 direction with being continuously recorded at anoverlap portion T. At the overlap portion T, the end point of the imageline 1 was overlapped with the start point of the image line 2, andthese image lines were continuously recorded.

Comparative Example B-2

Image recording and image erasing were performed in the same manner asin Example B-3 except that in the image recording step, a character of“V” was recorded in a continuous manner according to the recordingmethod as illustrated in FIG. 4C. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample B-3. Table 2 shows the evaluation results.

In the recording method as illustrated in FIG. 4C, the thermallyreversible recording medium was irradiated with the laser beam, and animage line 1 was recorded in a D1 direction. Then, an image line 2 wasrecorded in a D4 direction with being continuously recorded at anoverlap portion T. At the overlap portion T, the end point of the imageline 1 was overlapped with the start point of the image line 2, andthese image lines were continuously recorded.

TABLE 2 Number of repeatedly rewritable times At overlap At otherportions other I₁/I₂ at the time portion than overlap portion ofrecording Ex. B-1 430 520 1.75 Ex. B-2 470 560 1.65 Ex. B-3 560 650 1.75Ex. B-4 400 560 1.65 Ex. B-5 380 550 1.65 Ex. B-6 300 380 2.00 Ex. B-7300 370 0.40 Ex. B-8 150 220 2.05 ExB-.9 160 240 0.34 Ex. B-10 370 4601.60 Ex. B-11 470 560 1.60 Compara. 10 550 1.65 Ex. B-1 Compara. 10 6501.75 Ex. B-2

Example C-1

Using the thermally reversible recording medium of Production Example 3,image processing was performed as follows, and repetitive durability ofthe thermally reversible recording medium was evaluated. Table 3 showsthe evaluation results.

—Image Recording Step—

As a laser, a fiber-coupling high-powered laser diode device of laseroutput power 25 W (LIMO25-F100-DL808, manufactured by LIMO Co., centerwavelength: 808 nm, optical fiber core diameter: 100 μm, and lens NA:0.11) equipped with a condenser optical system of fθ lens (focaldistance: 150 mm) was used. The laser diode device was controlled suchthat the output power of the laser beam was 10 W, the irradiationdistance was 150 mm, and the spot diameter was about 0.75 mm. Then, acharacter of “V” was recorded on the thermally reversible recordingmedium of Production Example 3 at a photo-scanning speed of 1,200 mm/susing galvanomirrors according to the recording method illustrated inFIG. 10. Specifically, the thermally reversible recording medium wasirradiated with the laser beam, and an image 11 was recorded in a D1direction. Then, an image line 12 was recorded in a D4 direction withbeing continuously recorded at a folding portion T.

In the recording step, the image was recorded after controlling thelaser diode device such that at portions other than the start points andthe folding portion T of the image lines 11 and 12, the scanning speed(V) of the laser beam was set to 1,200 mm/s and the irradiation power(P) of the laser beam was set to 10 W; at the start point of the imageline 11, the laser beam began to be irradiated 0.3 ms after startingscanning with a mirror, the scanning speed was set to 1,500 mm/s, andthe irradiation power of the laser beam was set to 10 W; and at thefolding portion T, the scanning speed was set to 2,000 mm/s and theirradiation power was set to 10 W such that an actual P/V value could beconstant.

At that time, a light intensity distribution of the laser beam wasmeasured, and the ratio I₁/I₂ was 1.65.

—Image Erasing Step—

Subsequently, the laser diode device was controlled such that the outputpower of the laser beam was 20 W, the irradiation distance was 195 mm,the spot diameter was 3 mm, and the scanning speed was 1,000 mm/s. Then,the recorded image was erased while linearly scanning the laser beam at0.59 intervals. At that time, a light intensity distribution of thelaser beam was measured, and the ratio I₁/I₂ was 1.70.

<Evaluation of Repetitive Durability>

The image recording step and the image erasing step were repeatedlyperformed and finally, the erasing step was performed. Reflectancedensities of an erased portion at the overlap portion of the character“X” and portions other then the overlap portion on the thermallyreversible recording medium were measured to evaluate the image. Eachreflectance density was measured as follows. A gray scale image wasretrieved on a Gray Scale (manufactured by Kodak AG.) with a scanner(CANOSCAN4400, manufactured by Canon Inc.), the obtained digital grayscale values were correlated with density values measured by means of areflectance densitometer (RD-914, manufactured by Macbeth Co.).Specifically, a gray scale image of an erased portion where an image hadbeen recorded and then erased was retrieved with the scanner, and then adigital gray scale value of the obtained gray scale image was convertedinto a density value, and the density value was regarded as areflectance density value.

In the present invention, when a thermally reversible recording mediumhaving a thermally reversible recording layer which contained a resinand an organic low-molecular material was evaluated, and the density ofan erased portion was 0.15 or more, it was recognized that it waspossible to erase the recorded image, and when a thermally reversiblerecording medium having a thermally reversible recording layer whichcontained a leuco dye and a reversible developer was evaluated, and thedensity of an erased portion was 0.15 or less, it was recognized that itwas possible to erase the recorded image. Note that in the case of athermally reversible recording medium having a thermally reversiblerecording layer which contained a resin and an organic low-molecularmaterial, a reflectance density was measured after setting a black papersheet (O.D. value=1.7) under the thermally reversible recording medium.

The image recording step and the image erasing step were repeatedlyperformed, a reflectance density of an erased portion on the thermallyreversible recording medium was measured at every 10-time intervals ofthe image recording/image erasing, and the number of erasing times justbefore the recorded image could not be completely erased was determined.Table 3 shows the evaluation results.

<Measurement of Laser Beam Intensity Distribution>

A laser beam intensity distribution was measured according to thefollowing procedures.

When a laser diode device was used as a laser, first a laser beamanalyzer (SCORPION SCOR-20SCM, manufactured by Point Grey Research Co.)was set such that the irradiation distance was adjusted at the sameposition as in recording on the thermally reversible recording medium,the laser beam was attenuated using a beam splitter composed of atransmission mirror in combination with a filter (BEAMSTAR-FX-BEAMSPLITTER, manufactured by OPHIR Co.) so that the output power of thelaser beam was 3×10⁻⁶, and a light intensity of the laser beam wasmeasured using the laser beam analyzer. Next, the obtained laser beamintensity was three-dimensionally graphed to thereby obtain a lightintensity distribution of the laser beam.

When a CO₂ laser device was used as a laser, a laser beam emitted fromthe CO₂ laser device was attenuated using a Zn—Se wedge (LBS-100-1R-W,manufactured by Spiricon Inc.) and a CaF₂ filter (LBS-100-1R-F,manufactured by Spiricon Inc.), and a light intensity of the laser beamwas measured using a high-powered laser beam analyzer (LPK-CO₂-16,manufactured by Spiricon Inc.).

Example C-2

Image recording and image erasing were performed in the same manner asin Example C-1 except that the thermally reversible recording medium ofProduction Example 4 was used instead of the thermally reversiblerecording medium of Production Example 3. Repetitive durability of thethermally reversible recording medium was evaluated in the same manneras in Example C-1. Table 3 shows the evaluation results.

Example C-3

Image recording and image erasing were performed in the same manner asin Example C-1 except that the control conditions of the laser diodedevice was changed in the recording step. Repetitive durability of thethermally reversible recording medium was evaluated in the same manneras in Example C-1. Table 3 shows the evaluation results.

In the recording step, the image was recorded after controlling thelaser diode device such that at portions other than the start points andthe folding portion T of the image lines 11 and 12 as illustrated inFIG. 10, the scanning speed (V) of the laser beam was set to 1,200 mm/sand the irradiation power (P) of the laser beam was set to 10 W; at thestart point of the image line 11, the laser beam began to be irradiated0.3 ms after starting scanning with a mirror, the scanning speed was setto 1,200 mm/s, and the irradiation power of the laser beam was set to8.0 W; and at the folding portion T, the scanning speed was set to 1.200mm/s and the irradiation power was set to 6.0 W so that an actual P/Vvalue could be constant.

Example C-4

Image recording and image erasing were performed in the same manner asin Example C-1 except that in the image recording step, the focaldistance was changed to 160 mm, and the output power of the laser beamwas changed to 11 W. A ratio I₁/I₂ in the light intensity distributionof the laser beam was 2.00. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample C-1. Table 3 shows the evaluation results.

Example C-5

Image recording and image erasing were performed in the same manner asin Example C-1 except that in the image recording step, the focaldistance was changed to 144 mm, and the output power of the laser beamwas changed to 13 W. A ratio I₁/I₂ in the light intensity distributionof the laser beam was 0.40. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample C-1. Table 3 shows the evaluation results.

Example C-6

Image recording and image erasing were performed in the same manner asin Example C-1 except that in the image recording step, the focaldistance was changed to 163 mm, and the output power of the laser beamwas changed to 11 W. A ratio I¹/I² in the light intensity distributionof the laser beam was 2.05. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample C-1. Table 3 shows the evaluation results.

Example C-7

Image recording and image erasing were performed in the same manner asin Example C-2 except that in the image recording step, the focaldistance was changed to 143 mm, and the output power of the laser beamwas changed to 14 W. A ratio I₁/I₂ in the light intensity distributionof the laser beam was 0.34. Repetitive durability of the thermallyreversible recording medium was evaluated in the same manner as inExample C-2. Table 3 shows the evaluation results.

Example C-8 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam. The laser marker was controlled so that a ratio I₁/I₂ in the lightintensity distribution was 1.60.

Next, the laser marker was controlled so that the irradiation distancewas 198 mm, and the spot diameter was 0.65 mm. Then, using the lasermarker, a character of “V” was recorded on the thermally reversiblerecording medium of Production Example 1 according to the recordingmethod as illustrated in FIG. 10. In the recording step, the image wasrecorded after controlling the laser marker such that at portions otherthan the start points and the folding portion T of the image lines 11and 12, the scanning speed (V) of the laser beam was set to 1,000 mm/sand the irradiation power (P) of the laser beam was set to 14.0 W; atthe start point of the image line 11, the laser beam began to beirradiated 0.3 ms after starting scanning with a mirror, the scanningspeed was set to 1,700 mm/s, and the irradiation power of the laser beamwas set to 14.0 W; and at the folding portion T, the scanning speed wasset to 1.700 mm/s and the irradiation power was set to 14.0 W so that anactual P/V value could be constant.

<Image Erasing Step>

Subsequently, the mask for cutting a center part of a laser beam wasremoved from the optical path of the laser beam, and the laser diodedevice was controlled such that the output power of the laser beam was22 W, the irradiation distance was 155 mm, the spot diameter was about 2mm, and the scanning speed was 3,000 mm/s. Then, the image of thecharacter “V” recorded on the thermally reversible recording medium waserased.

Next, repetitive durability of the thermally reversible recording mediumwas evaluated in the same manner as in Example C-1. Table 3 shows theevaluation results.

Example C-9 Image Recording Step

Using a laser marker equipped with a CO₂ laser of output power of 40 W(LP-440, manufactured by SUNX Co., Ltd.), a mask for cutting a centerpart of a laser beam was incorporated in the optical path of the laserbeam. The laser marker was controlled so that a ratio I₁/I₂ in the lightintensity distribution was 1.60.

Next, the laser marker was controlled so that the irradiation distancewas 198 mm, and the spot diameter was 0.65 mm. Then, using the lasermarker, a character of “V” was recorded on the thermally reversiblerecording medium of Production Example 2 according to the recordingmethod as illustrated in FIG. 10.

In the recording step, the image was recorded after controlling thelaser marker such that at portions other than the start points and thefolding portion T of the image lines 11 and 12, the scanning speed (V)of the laser beam was set to 1,000 mm/s and the irradiation power (P) ofthe laser beam was set to 12.0 W; at the start point of the image line11, the laser beam began to be irradiated 0.3 ms after starting scanningwith a mirror, the scanning speed was set to 1,700 mm/s, and theirradiation power of the laser beam was set to 12.0 W; and at thefolding portion T, the scanning speed was set to 1.700 mm/s and theirradiation power was set to 12.0 W so that an actual P/V value could beconstant.

<Image Erasing Step>

Subsequently, the mask for cutting a center part of a laser beam wasremoved from the optical path of the laser beam, and the laser markerwas controlled such that the output power of the laser beam was 17 W,the irradiation distance was 155 mm, the spot diameter was about 2 mm,and the scanning speed was 3,000 mm/s. Then, the image of the character“V” recorded on the thermally reversible recording medium was erased.

Next, repetitive durability of the thermally reversible recording mediumwas evaluated in the same manner as in Example C-1. Table 3 shows theevaluation results.

Comparative Example C-1

Image recording and image erasing were performed in the same manner asin Example C-1 except that the scanning speed and the irradiation powerof the laser beam were not controlled at the start point and the foldingportion T of the image line 11 of a character of “V” as illustrated inFIG. 10. Repetitive durability of the thermally reversible recordingmedium was evaluated in the same manner as in Example C-1. Table 3 showsthe evaluation results.

Comparative Example C-2

Image recording and image erasing were performed in the same manner asin Example C-2 except that the scanning speed and the irradiation powerof the laser beam were not controlled at the start point and the foldingportion T of the image line 11 of a character of “V” as illustrated inFIG. 10. Repetitive durability of the thermally reversible recordingmedium was evaluated in the same manner as in Example C-2. Table 3 showsthe evaluation results.

TABLE 3 Number of repeatedly rewritable times at portions I₁/I₂ at theother than time start point and of at start point at folding portionfolding point recording Ex. C-1 530 480 560 1.65 Ex. C-2 630 590 6501.65 Ex. C-3 540 490 560 1.65 Ex. C-4 360 320 380 2.00 Ex. C-5 350 320370 0.40 Ex. C-6 200 150 220 2.05 Ex. C-7 230 160 240 0.34 Ex. C-8 450400 460 1.60 Ex. C-9 540 490 560 1.60 Compara. 150 10 550 1.65 Ex. C-1Compara. 190 10 650 1.65 Ex. C-2

Since the image processing method and the image processor of the presentinvention allow for repeatedly recording and erasing each high-contrastimage at high-speed on a thermally reversible recording medium in anon-contact manner and preventing deterioration of the thermallyreversible recording medium due to repeated image recording and imageerasing, the image processing method and the image processor can bewidely used in In-Out tickets, stickers for frozen meal containers,industrial products, various medical containers, and large screens andvarious displays for logistical management application use andproduction process management application use, and can be particularlysuitably used for thermally reversible recording media having a largearea, moving objects (movable objects) and in logistical/physicaldistribution systems.

1. An image processing method, comprising: any one of recording an imageon a thermally reversible recording medium that can reversibly changeany one of its transparency and color tone depending on temperature byirradiating and heating the thermally reversible recording medium with alaser beam, and erasing the image recorded on the thermally reversiblerecording medium by heating the thermally reversible recording medium,wherein in any one of the image recording and the image erasing, thethermally reversible recording medium is located at a position fartherthan a focal position of the laser beam, and at least any one of theimage recording and the image erasing is performed.
 2. The imageprocessing method according to claim 1, wherein when a distance from acondenser lens to the focal position is represented by “X” and adistance from the condenser lens to the thermally reversible recordingmedium is represented by “Y”, the equation, Y/X=1.02 to 2.0, issatisfied.
 3. The image processing method according to claim 1, whereinwhen a spot diameter of the laser beam at the focal position isrepresented by “A” and a spot diameter of the laser beam on thethermally reversible recording medium is represented by “B”, theequation, B/A=1.5 to 76, is satisfied.
 4. The image processing methodaccording to claim 1, used in image recording and image erasing on amovable object.
 5. The image processing method according to claim 1,wherein in a light intensity distribution of the laser beam irradiatedin any one of the image recording and the image erasing, a lightirradiation intensity I₁ at a center position of the irradiated laserbeam and a light irradiation intensity I₂ on an 80% light energybordering surface to the total light energy of the irradiated laser beamsatisfy the expression, 0.40≦I₁/I₂≦2.00.
 6. An image processing method,comprising: any one of recording an image on a thermally reversiblerecording medium that can reversibly change any one of its transparencyand color tone depending on temperature by irradiating and heating thethermally reversible recording medium with a laser beam, and erasing theimage recorded on the thermally reversible recording medium by heatingthe thermally reversible recording medium, wherein in the imagerecording, when an image having an overlap portion or overlap portionswhere a plurality of image lines are overlapped with each other is to berecorded, each of the image lines is recorded in a noncontinuous mannerat the overlap portion.
 7. The image processing method according toclaim 6, wherein the image is recorded so that at least one of a startpoint and an end point of each of the image lines is overlapped withanother image line at the overlap portion.
 8. The image processingmethod according to claim 6, wherein the image is recorded so that anend point of each of the image lines is overlapped with an end point ofanother image line at the overlap portion.
 9. The image processingmethod according to claim 6, wherein the image is recorded so that astart point of each of the image lines is not overlapped with anotherimage line.
 10. The image processing method according to claim 6,wherein in a light intensity distribution of the laser beam irradiatedin any one of the image recording and the image erasing, a lightirradiation intensity I₁ at a center position of the irradiated laserbeam and a light irradiation intensity I₂ on an 80% light energybordering surface to the total light energy of the irradiated laser beamsatisfy the expression, 0.40≦I₁/I₂≦2.00.
 11. An image processing method,comprising: any one of recording an image on a thermally reversiblerecording medium that can reversibly change any one of its transparencyand color tone depending on temperature by irradiating and heating thethermally reversible recording medium with a laser beam, and erasing theimage recorded on the thermally reversible recording medium by heatingthe thermally reversible recording medium, wherein in the imagerecording, at least one of a scanning speed and an irradiation power ofthe laser beam is controlled such that at least one of a laser beamirradiation energy per unit time and a laser beam irradiation energy perunit area in the thermally reversible recording medium is substantiallyconstant.
 12. The image processing method according to claim 11, whereinat least one of the scanning speed and the irradiation power of thelaser beam is controlled such that at least one of the laser beamirradiation energy per unit time and the laser beam irradiation energyper unit area at a start point, an end point, and a folding point ofeach of a plurality of image lines constituting an image issubstantially constant.
 13. The image processing method according toclaim 11, wherein at least one of the scanning speed and the irradiationpower of the laser beam is controlled such that a value of P/V, where“P” represents an irradiation power of the laser beam on the thermallyreversible recording medium, and “V” represents a scanning speed of thelaser beam on the thermally reversible recording medium, issubstantially constant.
 14. The image processing method according toclaim 11, wherein data of at least one of the scanning speed and theirradiation power of the laser beam controlled such that at least one ofthe laser beam irradiation energy per unit time and the laser beamirradiation energy per unit area in the thermally reversible recordingmedium is substantially constant is previously stored, and then theimage is recorded based on the data.
 15. The image processing methodaccording to claim 11, wherein in a light intensity distribution of thelaser beam irradiated in any one of the image recording and the imageerasing, a light irradiation intensity I₁ at a center position of theirradiated laser beam and a light irradiation intensity I₂ on an 80%light energy bordering surface to the total light energy of theirradiated laser beam satisfy the expression, 0.40≦I₁/I₂≦2.00.
 16. Theimage processing method according to claim 6, wherein each of theplurality of image lines is a line constituting any one of a character,a symbol and a diagram.
 17. The image processing method according toclaim 1, wherein the thermally reversible recording medium has at leasta thermally reversible recording layer on a substrate, and the thermallyreversible recording layer reversibly changes any one of itstransparency and color tone at between a first specific temperature anda second specific temperature that is higher than the first specifictemperature.
 18. The image processing method according to claim 1,wherein the thermally reversible recording medium has at least areversible thermosensitive recording layer on a substrate, and thereversible thermosensitive recording layer comprises a resin and anorganic low-molecular material.
 19. The image processing methodaccording to claim 1, wherein the thermally reversible recording mediumhas at least a reversible thermosensitive recording layer on asubstrate, and the reversible thermosensitive recording layer comprisesa leuco dye and a reversible developer.
 20. An image processor,comprising: a laser beam emitting unit, and a light irradiationintensity controlling unit that is placed on a laser beam emittingsurface and is configured to change the light irradiation intensity of alaser beam, wherein the image processor is used in an image processingmethod which comprises any one of recording an image on a thermallyreversible recording medium that can reversibly change any one of itstransparency and color tone depending on temperature by irradiating andheating the thermally reversible recording medium with a laser beam, anderasing the image recorded on the thermally reversible recording medium,wherein in any one of the image recording and the image erasing, thethermally reversible recording medium is located at a position fartherthan a focal position of the laser beam, and at least any one of theimage recording and the image erasing is performed.
 21. The imageprocessor according to claim 20, wherein the light irradiation intensitycontrolling unit is at least any one of a lens, a filter, a mask, amirror and a fiber-coupling device.